DE3120898A1 - MIXTURES OF POLYETHYLENE-TEREPHTHALATE-BASED POLYESTERS AND STYROL-MALEINIC ACID ANHYDRIDE COPOLYMERS - Google Patents

Description

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Mixtures of polyesters based on polyethylene terephthalate and styrene-maleic anhydride copolymers

Linear polyesters and copolyesters made from glycols and terephthalic or isophthalic acid, which have a high molecular weight, have been available for a number of years. They are described, among others, by Whinfield et al, U.S. Patent 2,465,319, and by Pengilly, U.S. Patent 3,047,539. These patents disclose that the polyesters have particular advantages as film and fiber formers exhibit.

Most widely used polyester made from these teachings is polyethylene terephthalate (PET). The success of this polymer in film and fiber applications is due in part to the significant improvement in properties brought about by stretching or stretching the films and fibers is effected, the polymer being obtained in an oriented, crystallized, morphologically advantageous form. Even though However, these polyesters are characterized by excellent mechanical properties, resistance to chemical They are characterized by attack, easy malleability and a tempting price, so far they are only available to a very limited extent for production three-dimensional objects have been used by means of various molding techniques.

The limited uptake that polyethylene terephthalate has so far found as a molding resin can be attributed primarily to the taking place slowly and. non-uniform crystallization, and this natural property of the material is responsible for sticking to the mold, the tendency to form molded parts with inconsistent surface properties as well as the tendency for significant shrinkage in the mold, leading to the formation of warped articles Shape leads. Because of the low rate of crystallization, an increased rate of crystallization must be increased over a long period of time Deformation temperature above the freezing temperature (temperature

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temperature of the second order phase transition) so that a sufficient degree of internal crystallization is achieved. Without developing a certain crystalline structure, the molded part tends to be limp and rubbery in texture. The required application however, higher deformation temperatures over extended periods of time cause rapid and uneven shrinkage in the injection mold. The shape of the resulting object is therefore often distorted and deviates from that of the injection mold away. The control of the development of an appropriate crystalline structure is therefore only possible if the dimensional stability is in place is sacrificed.

Attempts to overcome the disadvantages of polyethylene terephthalate have focused primarily on targeted influencing concentrated in the crystalline structure, e.g. by using a two-stage deformation process or by Adding nucleating agents and controlling molecular weight. So became the properties of injection molded polyethylene terephthalate modified by the addition of polyolefins as discussed in U.S. Patents 3,361,848, 3,504,080 and 3,769,260 will. However, none of these polyolefins are copolymers of styrene and maleic anhydride. The usage of nucleating agents, however, has not found further widespread use, since they are only used in a narrow range of the processing temperature are effective and lead to inconsistencies in the resulting objects. During the familiarization reinforcing fibers, such as glass fibers, improves the quality of the physical properties of the resulting molded parts (See, e.g., U.S. Patent 3,368,995), these fibers do not reduce the non-uniformity described above at.

It has also been proposed, as discussed in U.S. Patent No. 3,629,366, to prepare a polyethylene terephthalate molding composition made from at least two polyethylene terephthalates with different viscosities.

Some other polyalkylene terephthalates other than polyethylene terephthalate, made from glycols with a higher number of carbon atoms, such as polybutylene terephthalate, have been used with better success than molding resins in the past because they have the property crystallize at a faster rate than polyethylene terephthalate, which means that it is easier to deform deformation conditions extending over a wide range has the consequence.

Such polyesters can also be replaced by additives such as styrene-maleic anhydride copolymers, has been modified to improve the mechanical strength properties of injection molded parts as set out in US Pat. No. 3,644,574. However, this patent also discloses that by the addition of the contemplated additives to polybutylene terephthalate, the improvements sought cannot be achieved if the polyester Is polyethylene terephthalate.

However, polyesters such as polybutylene terephthalate tend to be considerably more expensive than polyethylene terephthalate, what their distribution as forirth resins to a certain extent has restricted. In addition, polybutylene terephthalate has somewhat inferior mechanical properties with respect to the Molded parts made therefrom as polyethylene terephthalate, as well as a lower heat resistance.

Styrene-maleic anhydride copolymers are also available as additives for polycarbonate resins and unsaturated polyesters, as disclosed in U.S. Patents 3,862,998 and U.S. Pat 4,038,341.

Clearly distinguishable from the deformation properties of the Polyethylene terephthalate is its surface energy properties. Possess polyethylene terephthalate polyester very poor adhesive strength when they are in the form of fibers or films on various substrates,

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such as aluminum, copper, glass, steel, rubber, paper, wood, chromium, organic polymers, mica, asbestos and the like.

It is believed that the poor adhesion of the polyethylene terephthalate partly on its surface energy characteristics is based. For an analytical consideration, the surface energy characteristics of a fiber or a Consider a film made of a solid polymer as the sum of two separate, additive contributions, namely a dispersive (i.e. non-polar) and a polar (Keesom) contribution. The polar one Component or contribution comprises various types of dipole interactions and hydrogen bonds, which for the sake of simplicity are combined into a single term. Of the Contribution of the dispersion component to the surface energy of the polyethylene terephthalate b. Is about 93%, while the polar component contributes only about 7%. It is well known that a polymer in which the polar contribution to its surface energy is low relative to the dispersive member, generally has poor adhesive properties. As a result become the adhesive properties of a polyethylene terephthalate can be improved if this can be changed to increase the polar contribution to its surface energy will.

In the past the adhesive properties of polyesters were improved by the incorporation of polyolefins such as styrene, such as the ÜS-PS 3 657 389 for the production of a hot melt adhesive explained. However, none of the polyolefins described in this patent are copolymers Styrene and maleic anhydride.

For the reasons given, ways of modifying certain polyesters such as polyethylene terephthalate have been sought continued with the aim of improving their ductility and adhesive properties. The present invention is a result of this search.

Accordingly, it is an object of the present invention to provide a polyethylene terephthalate-based polyester to make that deforms under economically favorable conditions can be and thereby provides a product that has improved mechanical properties, dimensional stability and shows easier deformability.

Another object of the present invention is to improve the adhesive properties of a polyethylene terephthalate-based polyester.

These and other objects and features of the present invention will become apparent from the claims and the following description in FIG Connection with the attached drawing recognizable.

An object of the present invention is a preparation consisting of a mixture of (1) a polyester, which at least Contains 85 mole percent polyethylene terephthalate, and (2) a styrene-maleic anhydride copolymer, which thereby is characterized in that the weight ratio of the polyester to the styrene-maleic anhydride copolymer in the Mixture of about 99: 1 each up to about 50:50 each

20 is.

Another object of the present invention is a method to improve the deformability of a polyester containing at least 85 mol percent polyethylene terephthalate, which is characterized in that this polyester with such an amount of a styrene-maleic anhydride copolymer is intimately mixed that the weight ratio of the polyester to the styrene-maleic anhydride copolymer in this mixture is from about 95: 5 to about 50:50.

Another object of the present invention is a method for deforming at least 8 5 mol percent polyethylene terephthalate containing polyester, which is characterized in that this polyester with such an amount

a styrene-maleic anhydride copolymer is intimately mixed so that the weight ratio of the polyester to the styrene-maleic anhydride copolymer is from about 95: 5 to about 50:50, and this mixture by means of a molding process using a temperature below the freezing temperature ( Temperature of the second order phase transition), but not below about 0 ⁰ C, is deformed.

Yet another object of the present invention is a method for improving the adhesive properties of a Polyester containing at least 85 mol percent polyethylene terephthalate, which is characterized in that this polyester with such an amount of a styrene-maleic anhydride copolymer is intimately mixed that the weight ratio of the polyester to the styrene-maleic anhydride copolymers

15 rises from about 99: 1 to about 80:20.

The attached drawing is a Kaelble diagram, that from the contact angles of a multiplicity of liquids which are applied to a multitude of film samples, manufactured by injection molding mixtures of polyethylene terephthalate and styrene-maleic anhydride copolymer, applied, was created.

The deformation and adhesive properties of certain polyesters are achieved by adding a styrene-maleic anhydride copolymer (SMA) improved.

In particular, the one used according to the present invention contains Polyester at least 85 mole percent, typically 85 to 100 mole percent, and preferably about. 90 to 100 molpro, cent polyethylene terephthalate. Thus, although the polyester is preferably composed of a homo-polyester in which the acid component different from the terephthalic acid and the glycol constituent is derived from ethylene glycol, copolyesters can also be used, in which the glycol component smaller amounts (i.e. no more than 15 mole percent in total

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the .Glycol total) may contain other glycols, such as e.g. diethylene glycol, neopentyl glycol, triethylene glycol, tetramethylene glycol, Hexamethylene glycol etc., and wherein the Acid constituent smaller amounts (i.e. no more than 15 percent of the total acid amount) of other dicarboxylic acids may contain, such as isophthalic acid, hexahydroterephthalic acid, diphenic acid, adipic acid, sebacic acid, Azelaic acid etc .. Accordingly, the abbreviation PET used here denotes both homo-polyester and copolyester, containing at least 85 mole percent polyethylene terephthalate.

The polyesters can be crystalline or amorphous. A typical example of an amorphous PET-based polyester consists of a random structure copolyester derived from (1) a mixture of neopentyl glycol and ethylene glycol and (2) terephthalic acid derived.

The polyester component of the blend can be prepared using any of the polymerization processes known in the art getting produced. For example, terephthalic acid or a dialkyl or diaryl ester of terephthalic acid (e.g. dimethyl terephthalate or diphenyl terephthalate) with ethylene glycol reacted and in this way the polyethylene terephthalate can be produced. A catalyst like e.g. antimony oxide is usually used during polymerization

25 tion used.

The polyethylene terephthalate-based component preferably has an intrinsic viscosity (IV) of about 0.5 to 1.0 dl / g and, in a particularly preferred embodiment, an intrinsic viscosity of 0.6 to 0.95 dl / g. The IV of the polymer can be determined using the equation lim r _ j _# -y _# , in which

(C - * - 0) C
lie "relatj
the viscosity of a dilute solution of the polymer

η denotes the "relative viscosity" obtained by dividing

- 11 -

the viscosity of the solvent used (measured at the same temperature) is obtained; C is the concentration of the polymer in the solution, given in g / 100 ml. The intrinsic viscosity can easily be determined using a solution of 0.1 g of the polymer in 100 ml of o-chlorophenol at 25 ° C. The polyethylene terephthalate usually shows a transition temperature of the glass-state of about 75 ° C and a melting point of about 25O ⁰ C to 265 ⁰ C, for example about 260 ⁰ C.

The ingredient to be added according to the present invention is a styrene-maleic anhydride copolymer.

The styrene-maleic anhydride copolymer used is a commercially available thermoplastic polymer well known in the art. The copolymer can with regard to its molecular weight and the quantitative ratio of the constituent constituents styrene and maleic anhydride can be varied over a wide range.

In general, the styrene-maleic anhydride copolymer by reaction of maleic anhydride with styrene at elevated temperatures, preferably in the presence a peroxide catalyst. Reference is made, for example, to US Pat. No. 2,971,939.

The molar ratio of styrene to maleic anhydride can be within can be varied over a wide range. Preference is given to using styrene-maleic anhydride copolymers in where the styrene: maleic anhydride molar ratio is on the order of about 1: 1 to about 15: 1, preferably from about 7: 1 to about 15: 1 (e.g. 13: 1). It will however, it is expressly pointed out that the copolymer also contain somewhat larger or somewhat smaller amounts of styrene

30 can. It should also be noted that the term

"Styrene-maleic anhydride copolymer" as used in this description and in the claims, including those Copolymers are understood, the substituents on the benzene

ring or wear on the alkenyl part of styrene, and also those copolymers which contain small amounts of other substances, such as α-methylstyrene, in the polymer chain. In addition, it should also be taken into account that mixtures in the preparations in the context of the present invention various styrene-maleic anhydride copolymers can be used.

The styrene-maleic anhydride copolymer should have a molecular weight are within the preferred range of about 2 to about 20,000;

The mixtures of the present invention can be prepared using any procedure suitable for initially preparing a substantially completely uniform mixture. A mixing process is preferably chosen in which there is practically no degradation of the molecules of the constituent constituents and which is carried out with the exclusion of moisture. The process of melt blending, in which the constituents are intimately mixed in the absence of moisture while they are kept at a temperature of about 250 ^° C. to 300 ^° C., is particularly suitable for this choice. The constituents can initially be mixed in the solid state (ie in the form of pellets or chips) and then subsequently mixed further in the melt to form an intimate mixture. In another way, the mixtures can be prepared in that the constituents polyester and styrene-maleic anhydride copolymer are dissolved in a suitable solvent, preferably a polar solvent, which, as described below, facilitates the surface enrichment, and then by precipitation (e.g. the mixture is obtained by adding a non-solvent) or by evaporating the solvent. The equipment suitable for producing the desired mixtures includes a plastigraph mixer, a melt extruder with one or more mixing chambers or any other device.

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processing, which is used for thorough mixing of polymeric materials in the melt or in solution is determined. After mixing, the resulting mixture can be pelletized or any other Application form are processed for further operations is required in accordance with the usual standard procedures. ■

The amount of styrene-maleic acid to be admixed with the polyester anhydride copolymer depends on the intended use of the mixture and on the addition of the copolymer for the purpose of the polyester to be fulfilled.

For example, if the styrene-maleic anhydride copolymer is added to the polyester to improve the adhesive properties will suffice to increase the polar contribution to the surface energy of the polyester, as explained above, amounts as low as 1% by weight of SMA copolymer, based on the weight of the two components of the mixture. For explanation, but without referring to any To establish a particular theory, it is assumed that the SMA in the PET / SMA Gemisehen with the polar groups whose surface is oriented rather than inside the mixture, as is normally the case with others containing polar groups Polymers is observed, and that the SMA copolymer accumulates on the solid surface of the polymer mixture. Thus, the change in surface energy caused by the SMA copolymer as a result of the surface enrichment and the Orientation of the polar groups can also be very pronounced when the SMA copolymer is only used in small amounts will.

If, on the other hand, the SMA copolymer is used to change the deformation properties of the polyester, it should it is used in amounts not less than about 5% by weight based on the weight of the two components of the mixture will. With an increasing content of SMA copolymer up to 50%, the deformation temperatures that to achieve satisfactory mechanical properties

can be applied, increasingly below the temperature of the second order phase transition can be lowered. Accordingly, the lower the deformation temperature becomes the less likely that shrinkage will occur. It becomes obvious in the special case To be used SMA content of the mixture are also influenced by the totality of those properties that the to be awarded by deforming the product to be manufactured.

Although any effective proportion of the SMA copolymer can be used on the mixture, such an effective amount is accordingly preferred that the Weight ratio of PET to SMA in the range from about 99: 1 to about 50:50, preferably from about 95: 5 to about 75:25, and more preferably from about 90:10 to about 80:20.

If the effect to be achieved is to improve adhesion, the effective weight ratios are PEI: SMA generally in the range of about 99: 1 to about 80:20 and preferably from about 95: 5 to about 90:10.

When the effect to be achieved is an improvement in deformability the blends in the sense that lower deformation temperatures can be used and thereby the shrinkage is reduced without adversely affecting mechanical properties, are the effective ones Weight ratios PET: SMA generally in the range from about 95: 5 to about 50:50, preferably from about 90:10 to about 80:20.

The improvements obtainable by modifying the polyethylene terephthalate in the polymer blends described herein with respect to the surface energy (i.e. the adhesive properties) are determined by wettability measurements and a surface energy analysis determines, whereby the dispersive and the polar contribution to the surface energy in the form of the

Surface tension solid-vapor can be separated from each other.

The polar and dispersive interaction when a liquid comes into contact with a solid can be described in detail express by the following mathematical relationships:

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w_ = γ '(1 + cos Θ) <2 γ ... (3)

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Mean therein

^ LV ⁼ ^ ■ • '" ^e ° ^ ^er surface tension of the liquid in the

Equilibrium with your vapor (surface tension liquid-vapor) in mN / m (dyn / cm); y _sv = the surface energy of the solid in equilibrium with the vapor of the liquid (surface tension solid-vapor); ⁰ L ^ L ^{= Q, inter alia, <ra} ^ ^{'t: seasoning} l ^ ^he corresponding polar (London) dispersive V _T ", and (Keesom) y £ \ ₇ parts of v _RT7; ctg ^ ₅ . = Square root of the corresponding dispersive>'

and polar y ^ _T7 proportions of γ _σ , _τ ; W = nominal imprisonment work;

α.

θ = contact angle liquid-solid.

From these relationships, the nominal work of adhesion W _a for a selection of liquids according to equation (3) is determined by measuring the contact angle (0) of each drop of the selected liquid, which was applied to the surface of the solid polymer mixture, which is in the form of a film Template. The liquids are chosen so that they differ to the extent that polar forces contribute to their interactions.

differentiate with the polyester surface. The values for the nominal work of adhesion W _a for each liquid are then inserted into equation (5), where α and ß _T from the literature values of γ n and

Ytjy to be calculated. The values obtained for each liquid on each film sample are then plotted on a single linear plot of W / 2α _τ (y-axis) versus ß _T / a _T (x-axis).

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gen. By extrapolating the straight line obtained to ß / a = 0

r \ 1 / O

α · = 0 'J' is obtained. The rise of the straight line provides the factor ß _c = (vS „). The analysis described above is referred to as the Kaelble method and is discussed in the publications cited below and incorporated herein by reference: DH Kaelble, Physical Chemistry of Adhesion, Wiley-Interscience, New York (1971), pp. 139-170; DH Kaelble, J. Adhesion 2 ^, 66 (1970); PJ Dynes and DH Kaelble, J. Adhesion £, 195 (1974); DH Kaelble et al, J. Adhesion ^, 239 (1974).

When analyzing the PET / SMA blends described herein after the Kaelble method is found to be the contribution of the polar Component for the surface energy of the solid mixture in equilibrium with the vapor of the selected liquids Compared to the polar part of the surface energy of the polyethylene terephthalate taken by itself considerable is increased. It has thus been found that the polar or dispersive contribution to the surface energy of the PET is taken on its own 2.88 itiN / m or 39.48 mN / m, while it is polar or the dispersive part of the surface energy of the PET / SMA mixtures amounts to 53.29 mN / m and 3.06 mN / m, respectively. this means an 88% increase in the contribution of the polar component to the total surface energy. In addition, it is believed that-ß the increase in the polarity of the device even at a low level Addition of the SMA, i.e. a high PET / SMA weight ratio of 99: 1, occurs because there is apparently enough SMA in the mixture finally migrates to the surface of the solid polymer mixture and is concentrated there, so that the described Conversion of polarity comes about. The surface

Enrichment is easiest when the PET / SMA mixture is used is melted. Accordingly, it is desirable to use a mixture because of its adhesive properties should find, to manufacture by means of a melt-blending process Such surface enrichment can also take place during paser or film production, where the mixture is based a temperature above the melting point of both components of the mixture is heated. Such a surface enrichment can also take place when the components of the mixture are dissolved in the same solution and this on a polar substrate is cast so that the polar groups' of the SMA are on the surface of the mixture that is associated with the substrate is in contact, are induced to orientate themselves by the attraction of the polar groups of the latter.

The change in polarity caused by the SMA copolymer increases the adhesive properties of the mixture.

With regard to the deformation properties of the PET / SMA blends, it has been found that the good mechanical properties of the molded parts, such as tensile strength, tensile modulus, flexural strength and flexural modulus, can be achieved without the mold being raised to a "temperature above the freezing temperature (temperature of the phase transition In the typical molding process, for example injection molding, a polymer is ^{heated to a temperature above its melting point, ie to about 280 °} C. to about 300 ^° C., and the molten polymer is removed from the heated chamber by hydraulic pressure driven into a closed mold. According to the prior art, the shell mold is usually kept in · case of the polyethylene terephthalate at a temperature of at least 140 ⁰ C and the polymer is approximately s left for a period of 40 in der'Hohlform. the heating of the mold is necessary to ensure complete crystallization of the polyethylene terephthalate sic to produce, since otherwise the polymer is slack and rubbery. If alterna-

tively, the mold is not heated, so the molding at a temperature of about 140 ⁰ C for periods up to two hours to be away annealed or heat-set, so that a complete crystallization and the development of good mechanical properties is ensured.

It has been found that in injection molding, in particular in injection molding, of PET / SMA mixtures, the temperature of the hollow mold can be selected to be variable ^{in a range below the glass transition temperature of the polyester to not less than 0 ° C., typically from about 0 °} C. to about 60 ⁰ C, preferably from about 2 ° C to about 25 ° C. Although the polymer mixture does not completely crystallize at these low mold temperatures, it has been found that complete crystallization is not necessary in order to achieve good mechanical properties. Accordingly, the moldings do not need to be post-tempered or thermoset, and since the mold temperature is kept below the glass transition temperature, the problem of shape distortion and shrinkage of the moldings is practically eliminated without affecting the mechanical properties. Another advantage of using SMA as an additive is that SMA is cheaper than PET. Correspondingly, the use of the PET / SMA mixtures also results in considerable cost savings.

In general, the PET / SMA blends according to the present invention Invention optionally contain one or more additional ingredients in even distribution, which as Nucleating agents, flame retardants, filler, dye or reinforcing material can serve. Such non-polyester ingredients can be added to the mixture at the same time in one operation during its production or also afterwards be incorporated. For example, a nucleating agent (1-10%), a flame retardant (10-20%), a Filler (1 - 50%), a dye (1 - 20%) or a reinforcement material (1 - 50%) in the percentages by weight, based on the weight of the polyester mixture components,

can be dispersed in the mixture at various concentrations. Suitable nucleating agents, flame retardants, fillers or Reinforcing materials can be of organic and / or inorganic origin and "particulate or fiber" form.

Particulate fillers are suitable for reducing the production costs of the mixtures and improving the mixtures to give aesthetic properties. To the suitable particles " shaped fillers include clays, silicates, phosphates etc .; their particle size is preferably in the range of 0.1 to 50 μΐπ.

Suitable fibrous reinforcing materials include glass fibers, Asbestos fibers, carbon fibers (e.g. graphite fibers) or any other high modulus reinforcement material. Such fibrous reinforcing materials are preferably in the form of individual short lengths with a slenderness ratio (aspect ratio) of at least 10 to be used, but can also show relatively continuous expansion in relation to the length. The fibrous reinforcement materials aim to further improve the module, the consolidation

20 speed and the dimensional stability of the mixture.

Halogen or phosphorus-containing substances can be added to the mixtures to make them flame retardant. Asbestos and other similar materials can be used to reduce dripping and burning when exposed to a flame. Commercially available drip retardants include a polytetrafluoroethylene, preferably of large particle size. Suitable nucleating agents include finely divided inorganic or polymeric substances such as talc, sodium silicate _and polypropylene, etc., whereby the particle size is preferably less than

30 half of 2 μπι is.

Filler, reinforcing material or other additives can be used the polyester mixture expediently immediately during its production or afterwards, as long as the mixture is used

is still melted.

The blends according to the present invention show improved physical properties and properties as well, which differ significantly from what experts would expect. From the mixtures described herein With the help of conventional melt manufacturing processes, fibers, films or three-dimensionally shaped Objects are made.

Fibers can be made by conventional melt spinning. For example, threads can with economically interesting properties at melt temperatures of about 255 ⁰ C to 280 ⁰ C and spinning speeds of about 305 to 457.5 m / min. and subsequently hot drawing at about 80 ⁰ C to 100 ⁰ C at a draw ratio of about 2.5: 1 to about 6: 1 are prepared, in a similar manner conventional films can be prepared Schmelzgieß or melt-extrusion method using.

Three-dimensional objects can be made using any conventional injection molding machine. Typical injection molding conditions include a melt temperature of about 26O ⁰ C to about 300 ⁰ C, mold temperatures as described herein, shot-times of about 15 to. about 30 s; the screw rotation speeds can typically range from about 60 to 90 minutes and the injection pressures can be selected from about 552 to 897 bar (8,000 to 13,000 psi) as usual.

The good adhesive properties brought about by the highly polar surfaces of the blends described herein make them particularly suitable for use as tire cord because they bond well with rubber. Films made from the mixtures exhibit good adhesion to both polar and polar non-polar substrates such as steel, aluminum, chrome, glass, paper, wood, organic polymers, mica and asbestos;

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for this reason, such films can be used as packaging films as well as for all possible uses for mono- and biaxially stretched films, e.g. as bases for photographic Films, for audio tapes and for adhesive tapes.

The most important and most widespread uses the mixtures according to the present invention are in the field of making more attractive, more economical three-dimensional objects with a rigid shape and smooth surface. Surprisingly, such show three-dimensional Objects have a smooth, shiny surface texture and behave tough and bouncy. The smooth, glossy surface finish also generally remains then obtained when in the material of the molded article glass fibers or other fibrous reinforcing materials

15 are incorporated.

To the typical manufacturable three-dimensional objects include those that are manufactured by injection molding, compression molding, injection molding, molding by foaming and hot foaming, as well as also layered molded parts.

The present invention is illustrated by the following examples, describe the preferred embodiments, explained in more detail. All mentioned in the examples as well as in the description Unless otherwise stated, parts and percentages are based on weight.

- 22 Example .1

A polyethylene terephthalate (PET) is selected, which is produced by melt polymerization of terephthalic acid with polyethylene glycol and has an intrinsic viscosity as described above of about 0.9 dl / g.

A styrene-maleic anhydride copolymer, which according to conventional Process with a styrene / maleic anhydride ratio of 93: 7 and manufactured by Arco Polymers

TM is available under the trade name "Dylark 232", is granulated and mechanically mixed with the aforesaid, also previously granulated polyethylene terephthalate in various PET / SMA weight ratios, as indicated in Table I. Each of these mechanical mixtures is dried in a vacuum oven at about 100 ^° C. and in an extruder with screw feed (Plasti-Corder from CW

Barbender Instruments, Ine.) Into strands which are cut into pellets about 3.2 mm (1/8 inch) in diameter. The pellets are processed dried in an oven at 100 ⁰ C overnight, and by injection molding in molds, which were maintained at a temperature of about 4.5 ⁰ C into test bars. Each of these test bars as well as a comparison bar consisting exclusively of polyethylene terephthalate is examined for tensile strength and tensile modulus (according to ASTM D 638) as well as flexural strength and flexural modulus (according to ASTM D 790). the

Table I shows 25 results.

As can be seen from the data in Table I, the PET from test 5 ^{cannot be tested when the mold temperature is 4.5 °} C. because it is slack and rubbery. "Accordingly, 'was Experiment 6 carried out at a temperature of the hollow form of 14O ⁰ C, thereby pie sample obtained provides a basis for comparison of the mechanical properties of the various mixtures with the mold-injected in a conventional manner PET for testing. The mechanical properties of the samples of Experiments 1 to 4 are with those of the sample

of experiment 6 comparable. In experiments 1 to 4 it was No shrinkage of the samples was observed.

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- 24 - '· - · · - · - "· -" ■ Example 2

Example 1 is repeated with the modification that in the PET / SMA mixtures 30% by weight of glass fibers with a length of about 4.76 mm (3/16 inch) had been incorporated. The results are summarized in Table II.

As can be seen from the data in Table II, the The mechanical properties of the injection-molded rods are even further improved by the incorporation of the glass fibers.

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CN

co

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ro

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Notes to Table II ;

(*) according to ASTM D 638;

(**) according to ASTM D 256;

(***) according to ASTM D 648.

5. Example 3

The following example serves to illustrate the effect of mixing an SMA copolymer with polyethylene terephthalate on the surface energy characteristics of the resulting mixture.

Granules made of polyethylene terephthalate and those made of styrene-maleic anhydride are mechanically mixed in various PET / SMA weight ratios and extruded into pellets according to Example 1. The pellets are then compression molded at 28 0 ⁰ C between Kapton sheets into sheets of 0.25 mm (10 mil) thickness. Each of these films is subjected to a Kaelble analysis as described above. This is carried out in detail as follows: Each film sample is placed on a slide to keep it level. A drop of liquid with suitable surface tension is applied to the surface of each film sample using a 1 cm -Fisherbrand injection syringe, and the contact angle at the three-phase boundary liquid-solid-air is measured directly in degrees using a Rame-Hart contact angle goniometer measured. A second and third drop of the same liquid is added to the first, and after each addition the angle is measured again. This procedure becomes two-up. repeated four times until an exact mean value for the contact angle of a particular liquid is obtained, which can be seen from the fact that the contact angles measured continuously after each additional addition coincide within a few degrees. The observed contact angles for double distilled water, formamide, methylene iodide, PG-P-1200 (a poly-

glycol, available from Dow Chemical Co.) and ethylene glycol are listed in Table III along with the corresponding PET / SMA weight ratios for each film sample. The contact angles are arranged in Table III in such a way that the values in a row correspond to a single series of successive drops which have been applied to the same point on the film. Each series of contact angles relates to a different location on the film to which the series of drops is applied. The mean contact angle of each liquid on each foil is used to calculate the value W / 2oi _ according to equation (3),

a L

and the values obtained for each liquid are plotted as ordinate (y) values on a Kaelble diagram as shown in the figure. The literature values of each liquid for ß _T and cc are used to establish ß _T / oc and

Li Jj Li Li

2 ex.- used as given in Table III. The value

ß _T / <* is used as the abscissa value (x-) of each liquid.

Xj Lj

The value 2 <* takes place in connection with the contact angles

Lj

to determine the ordinate values use. The values of W / 2 oc determined for each solvent at three different

CL. Xj

those blend compositions are listed in Table IV. The angles of contact and ordinate values that result from it were determined for methylene iodide are discarded when determining the straight line, since it was found that methylene with reacts to the film samples.

A single straight line is determined from the individual values, which represents the three film samples with different PET / SMA weight ratios. The slope of the straight line, ie β _o , is determined from the graphic representation reproduced by the figure to be 7.30, while the section on the y-axis, ie ¹ ^ ₀ , is found to be 1.75. From the squares of the two values for the slope and the ordinate value at

'_ 0 the abscissa of the graph are the polar (γ ^] and the dispersive () f _ςν) proportion of the solid-vapor surface tension 53.29 mN / m and 3.06 mN / m sawn

is correct, so that the total surface tension value () ' _OT J

56.35 mN / m. The corresponding values for pure PET are 2.88 mN / m () '| _y ) and 36.59 mN / m (Vg _V ). The above values show that the polarity, i.e. the quotient F ^ / V ,

DV Ov

on the surface of the PET film by adding the styrene-maleic anhydride copolymer is increased from 0.07 to 0.95. This is caused by a significant increase in the polar component, in the surface energy of the PET mixed product. Thus, it is believed that the variation in surface properties of the film samples at each PET / SMA ratio by the concentration of the styrene-maleic anhydride is caused on the surface of the film due to a phenomenon known as surface enrichment, and by orienting the polar groups to the outside as described herein. Such a surface enrichment takes place even at low SMA concentrations. Accordingly, even the addition of a small one has the effect Amount of SMA to the PTE actually causes a large change in the properties of the solid surface of this material.

Table III

Liquid contact angle

Ver PET / D, L. middle 41 « Dest . H 7 ° '3 Formamide = 0. 90 search SMA 3 40 ^e values 40 ' Va- = 1. 53 / αν ^: = 11. 37 Weight - 38 ^C 50/50 37 ' Zq, _t ⁼ 9. 34 54 ^C ; JLj 58 ° 62 ° Relation 44 ^C 44 ' '43 ° 43 ° 45 ° 65 ^{C 1} 58 ° 63 ° 63 ° 1 90/10 51 ^C 41 '42 ° 40 ° 41 ° 55 ^C '65 ° 59 ° 59 ° 48 ^C > ₄₅ o 45 ° 45 ° 59 < '57 ° 58 ° 61 ° ¹ 52 ° 55 ° 56 ° 61 * > 53 ° 61 ° 61 ^ό > ₄₈ ° 52 ° 48 ° ⁵ 61 ° 65 46. 05 58 ' 59. 59 ° 59 ° ⁵ 41 ° 43 ^C '46 ° 59 ' ^s 58 ° 59 ° 57 ° 2 = »40 ° 38 ^C '37 ° 55 ' ⁰ 59 ° 51 ° 53 ° ⁰ 40 ° 41 ^{C 1} 43 ° 4g 0 490 51 ° 48 ° ⁰ 46 ° 45 ' ¹ 46 ° 53 ° 50 ° 54 ° 53 ° 0 4 ^ p 49 ^C > / IQO 0 540

β _τ / α ^L

= 0 »22 = 13.93

52 ° 47 ° 45 ° 45 °

40 ° 44 ° 44 ° 44 °

50 ° 43 ° 45 ° 41 °

54 ° 54 ° 47 ° 48 °

PG-P-1200 ß_ / a, = 0.5 3 ^L ^ = 9.90

30 ° 27 ° 29 ° 29 °

34 ° 29 ° 32 ° 34 °

37 ° 40 ° 40 ° 40 °

34 ° 23 ° 24 ° 27 °

42 ° 40 ° 42 ° 42 °

33.75

Ethylene - glycol β / α, = 0.81 ^L ^ = 10.8

45 ° 48 ° 56 ° 58 ° 60 ° 61 ° 62 ° 62 ° 58 ° 60 ° 58 ° 58 ° 59 ° 59 ° 59 °

5.7.90

Mean values

42.40

54.40

21 ° 21 ° 25 ° 28 °

28 ° 23 ° 20 ° 16 °

29 ° 28 ° 31 ° 25 °

27 ° 29 ° 39 ° 46 °

26 ° 25 ° 25 ° 40 °

18 ° 24 ° 24 ° 24 ° 16 ° 14 ° 19 ° 20 ° 18 ° 24 ° 22 ° 18 °

20.0 8

45 ° 4'4 ° 43 ° 51 ° 53 ° 51 ° 44 ° 50 ° 56 °

48.58

iu / yu 46 ° middle 48 ° 48 ° 49 ° 43 ° values 45 ^Ö 37 ° 42 ° 46 ° 49 ° 46 ° 46 ° 42 ° 49 ° 49 ° 47 ° 49 ° 49 ° 51 ° 51 ° cn

64 ° 64 ° 60 ° 61 °

58 ° 58 ° 58 ° 58 °

60 ° 61 ° 60 ° 58 °

60 ° 58 ° 60 ° 63 °

63 ° 65 ° 59 ° 59 °

60.35

21 ° 32 ° 31 ° 31 °

21 ° - - 22 °

29 ° 29 ° 34 ° 43 °

29 ° 22 ° 26 ° 31 °

27 ° 28 ° 24 ° 25 °

10 ° 12 ° 13 ° 16 ° 12 ° 14 ° 11 ° 13 ° 14 ° 16 ° 16 ° 15 ° 17 ° 19 ° 19 ° 18 ° 10 ° 17 ° 21 ° 20 °

15.15

31 ° 27 ° 27 ° 25 ° t 40 ° 49 ° 47 ° 51, ° *. 51 ° 50 ° 54 ° 5%, ° ,,

42.08

co co cc

Table IV

■ Wa / 2a.

PET / SMA

D. Pest. H O formamide

90:10

13.20

7.72

6.16

50:50

13.55

8.10

6.88

10:90

13.15

7.66

6.86

PG-P-1200 ethylene-glycol

5.79 6.13 6.21

6.83 7.41 7.77

K) O OD CO CO

Claims (1)

Claims 1. Preparation consisting of a mixture of (1) one polyester containing at least 85 mol percent polyethylene terephthalate and (2) a styrene-maleic anhydride copolymer, characterized in that the weight ratio of the polyester to the styrene-maleic anhydride copolymer of about 99: 1 each up to about 50:50 each. 2. Preparation according to claim 1, characterized in that the weight ratio of the polyester to the styrene-maleic anhydride copolymer from about 95: 5 to to about 75:25. 3. Preparation according to claim 1, characterized in that the polyester is a homopolymer of polyethylene terephthalate. Telephone: (0221) 131041 Telex: 8882307 dopa d - Telegram: Dömpatent Cologne 4. Method for improving the deformability of at least one 85 mole percent polyethylene terephthalate-containing polyester, characterized in that this polyester with a styrene-maleic anhydride copolymer is intimately mixed so that the weight ratio of the polyester in this mixture to the styrene-maleic anhydride copolymer is from about 95: 5 to about 50: 50. 5. The method according to claim 4, characterized in that the polyester is a homopolymer of polyethylene terephthalate and the mentioned weight ratio is from about 90:10 to about 80:20. 6. A method for shaping a polyester containing at least 85 mol percent polyethylene terephthalate, characterized in that (1) this polyester is intimately mixed with a styrene-maleic anhydride copolymer, so that in this mixture the weight ratio of the polyester to the styrene-maleic anhydride Copolymer is from about 95: 5 to about 50:50, and (2) this mixture is shaped by means of a shaping process using a temperature below the glass transition temperature (temperature of the second order phase transition), but not below about 0 ^° C. 7. The method according to claim 6, characterized in that the polyester is a homopolymer of polyethylene terephthalate, the weight ratio is about 90:10 to about 80:20, the mixture is made by melt blending and the deformation temperature is from about 0 ° C to about 60 ° C. 3. Process to improve the adhesive properties of a minor * at least 85 mole percent polyethylene terephthalate-containing polyester, characterized in that this polyester with a Styrene-maleic anhydride copolymer is intimately mixed, so that the weight ratio of the polyester to the styrene-maleic anhydride copolymer is from about 99: 1 to about 80:20. 9. The method according to claim 8, characterized in that the mentioned polyester a homopolymer of polyethylene terephthalate the weight ratio is from about 95: 5 to about 90:10 and the preparation of the mixture by melt blending of the two components takes place.