WO1991011489A1

WO1991011489A1 - Endless objects from acrylates

Info

Publication number: WO1991011489A1
Application number: PCT/NL1991/000014
Authority: WO
Inventors: Cornelis Wilhelmus Maria Bastiaansen
Original assignee: Dsm N.V.
Priority date: 1990-02-02
Filing date: 1991-02-01
Publication date: 1991-08-08
Also published as: NL9000258A; JPH05505631A; EP0515401A1; AU7147191A

Abstract

Oligomeric acrylates containing composition suitable for the production of endless objects without the use of continuous carrier material, whereby the composition also contains a high molecular weight thermoplastic polymer. Products made from a composition according to the invention are, depending on the starting materials, suitable for applications in those areas where a good temperature resistance, a good fire resistance and/or a good corrosion and solvent resistance are required besides good mechanical properties. Examples are cable sheathing, fireproof clothing, asbestos replacement, high temperature filters, aircraft interiors, precursors for carbon fibre, food packagings (for instance for use in a microwave oven), condenser films, optical fibre and filament winding products.

Description

ENDLESS OBJECTS FROM ACRYLATES

The invention relates to an oligomeric acrylates containing composition suitable for the production of endless objects without the use of carrier material. By 'endless objects' are understood in the present specification objects that have a virtually infinite length in at least one direction, such as fibres, sheets and tubes. By a 'carrier material' is understood material which potentially is infinitely long, such as filaments or films, and onto which the acrylates containing composition is applied and then cured. This could be a thermoplastic foil or fiber.

A composition from^hich endless objects can be made without using carried material is described in JP-A-61262707.

It describes a composition on the basis of acrylates which by a special treatment can be processed to endless objects, in particular to optical fibres. To accomplish this, a set-up is built in which an acrylate mixture is pressed through i ^ltube, the acrylates being partially cured in the tube, after which the partially cured acrylates are spun and cured further.

The drawback of a composition as described in JP-A-61262707 is that a complicated treatment is required in order to be able to process the oligomeric acrylates continuously, because the acrylates have to be cured partially but must not reach their gel point. The range within which the acrylates can be processed continuously consequently is rather narrow. This requires accurate adjustment of the process conditions and continuous checking of the degree of curing during the transport through the tube. Consequently it is a very slow, laborious and thereby costly process, and in any case very sensitive to disturbances.

The aim of the invention is to provide a composition which does not have said drawbacks and from which therefor easily endless objects can be produced.

According to the invention this is achieved owing to the composition additionally containing a high molecular weight thermoplastic polymer. By 'high molecular weight' (HMW) is meant here higher than 50,000 g/mol. Preferably the molecular weight of the thermoplast is even much higher than 50,000, e.g. 250.000 and higher. If the thermoplast has a molecular weight of more than 250,000 g/mol, it is considered to have an 'ultrahigh molecular weight' (UHMW) .

Owing to mixing in of HMW thermoplast, the composition can for instance be processed and formed in an extruder. Moreover, the composition can be stretched, either in one or in two directions. In this way fibres or sheets for instance can be produced.

Another difference between a composition described in JP-A-61262707 and the invention is that the composition according to the invention need not be cured until after the spinning or the processing in the extruder, while the composition according to JP-A-61262707 is already partially cured before the spinning.

The spinnability will be used as criterion of the continuous processability in the manner as set out here. If a composition is spinnable, it can presumably also be processed to other forms of endless objects besides fibers. The concept of spinnability is difficult to quantify, but in the present specification the definition as given by Ziabicki in 'Fundamentals of Fibre Formation', J. Wiley & Sons Ltd., London, 1976, will be used: 'A liquid is spinnable under the given conditions if a steady-state, continuous elongation of the fluid jet proceeds without a break of ariy kind'.

By 'the given conditions' are meant here the conditions optimized by one skilled in the art.

In the experiments the spinnability is tested by determining whether a thread picked up with a glass rod from a quantity of test material can be elongated and wound around a small spindle. This test is described by Ziabicki in the same reference.

The degree of change of the spinnability depends, among other factors, on the molecular weight of the thermoplast. The higher the molecular weight, the less material has to be added to cause the viscosity to be enhanced by a certain degree in order to make the composition spinnable.

The spinnability test as performed in the experiments which follow are not intended to exclude all non-working amounts of mixtures of monomers and thermoplast, but are intended to indicate that a certain amount is preferred under certain circumstances. By routine experimentation it is possible to adapt the circumstances (e.g. the temperature) of most experiments in such a way that a composition is spinnable.

The thermoplast is preferably at least partially solved in the acrylate monomers.

In general, it will be advantageous to add the thermoplast as little particles with a diameter of less then 0.5 mm, because this improves the speed of solvation of the thermoplast in the monomers. It is also possible to heat the thermoplastic before it is added to the composition. It has to be said that a fast solvation speed is not necessary for a succesful application of a composition according to the invention.

The composition preferably contains, relative to the composition as a whole, at least 0.1 wt.% thermoplastic polymer with an MW of more than 5,000,000 and up to about 50 wt.% with an MW of about 50,000.

The composition more preferably contains, relative to the composition as a whole, at least .0,1 wt.% . .. thermoplastic polymer with a molecular weight of more than 5.000.000 and up to at least 2.5 wt.% of the thermoplastic polymer with a molecular weight of 900.000.

The minimum quantity of thermoplast to be added in order to obtain a continuously processable composition also depends on the type of thermoplast: in general, of ther oplasts that are high viscous above their melting point, a lower quantity will be needed then of thermoplast that are low viscous above their melting point. For instance, in general a higher quantity of a branched thermoplast than of a linear thermoplast will be required. In general the desired properties of the composition will be determined by the average chain length of the thermoplastic polymer dissolved in it. This means for instance that of polyethylene oxide (PEO) a lower weight percentage with a certain molecular weight will suffice than of polyvinyl acetate (PVA), because PEO is less heavy than PVA per unit of chain length because PEO has no side-chains while PVA has. It is possible to add higher percentages of thermoplast. However, the properties of the product may be adversely affected by the thermoplast. Therefore it is mostly desirable to keep the quantity of thermoplast as small as possible. Mixing in of a thermoplast in a liquid for polymerization in order to increase the viscosity is described in GB-A-1,057,434, which does not refer to oligomeric acrylates however. The aim of that patent specification is to provide a solution to the problem of a polymer not solving in its own monomers. There is no suggestion in the patent specification that it would also work with thermosetting systems on the basis of oligomeric acrylates.

cyclohexyl, p-bromophenyl methacrylate, 2,3-dibromopropyl methacrylate, 1-methyl-cyclohexyl methacrylate, n-hexyl methacrylate, β-brbmoethyl methacrylate, methyl α-chloroacrylate, β-naphthyl methacrylate, N-n-butyl-methacrylamide, methacrylmethyl salicylate, ethylene glycol monomethacrylate, n-benzyl-methacrylamide, β-phenyl-sulfonethyl methacrylate, n-methyl-methacrylamide, N-allyl-methacrylamide, methacrylphenyl salicylate, N-p-methoxyeth l methacryla ide, N-β-phenyl-ethyl methacrylamide, cyclohexyl α-ethoxy-acrylate, 1,3-dichloropropyl 2-methacrylate, 2-methyl-cyclohexyl methacrylate, 3-methyl-cyclohexyl methacrylate, 4-methyl-cyclohexyl methacrylate, 3,3,5-trimethyl-cyclohexyl methacrylate, floruenyl methacrylate and/or α-naphthylcarbinyl methacrylate.

It is possible to at least partly add monomeric acrylates to the composition. By differing the ratio of the oligomeric acrylates and the monomeric acrylates, the properties of the product can be influenced. Also other co-polymerisable monomers can be added.

The thermoplast should at least partially dissolve in the oligomeric acrylates. Depending on the choice of thermoplast and acrylates and the rate of curing, a molecular blend is obtained or a crystallisation or a phase separation takes place upon curing. The latter may give rise to favourable properties, such as improved toughness of the final product. This may be due to the glass transition temperature (Tg) of the thermoplast being lower than the service temperature. If such phenomenon is unwanted, the process conditions can be adapted such that it does not occur, e.g. by enhancing the spinning temperature.

Low molecular thermoplasts may further be added to the composition to improve certain properties, such as the impact resistance.

The usual additives may further be taken up in the composition, such as inhibitors, promoters, accelerators, flexibilizers, lubricants, release agents, antioxidants, pigments, surfactants, crosslinkers, fillers or fibre reinforcement agents. Initiation of the curing may be effected in all ways by which acrylates can be cured, such as thermally, with UV light, with other electromagnetic radiation or with electron or gamma radiation.

Preferably, the curing takes place under the influence of UV light, because then the curing can be effected simply. Also, the time can be chosen freely then: during or after the shaping process or during the cooling stage. An additional advantage is that then during the suspending, dissolving and extruding or spinning high temperatures are possible, without causing the curing to start already.

A possible mode of operation for a process for the manufacture of products is the following:

The thermoplast is suspended and dissolved in the acrylates. This may require heating of the composition to a suitable temperature, for instance between 50 and 200°C. Preferably the composition is not heated to a temperature at which one or more of the components start to boil. The mixture is then extruded or spun and then partially or fully cured.

Additional steps in this mode of operation can be mixing in of strengthening fibres in the composition and stretching of the extruded or spun semimanufacture.

With strenthening fibers is meant, according to the invention, fibers that have properties that are such that they improve the properties of the product in which those fibers are incorporated. Strengthening fibers will normally not melt or otherwise loose their mechanical strength under the processing conditions. Examples are glass fibers and carbonfibers, but any other fiber can be used principally. The viscoelasticity of the composition can be set in dependence on the chosen method of processing. If spinning in a downward direction is opted for, a lower weight percentage or a lower molecular weight thermoplast will suffice than in the case of for instance film blowing in an upward direction. If it is intended to produce thin objects, it is recommendable to stretch the composition, before the curing. If fibrous fillers have been added, which are required to be in oriented condition in the product, it is also recommendable to stretch the composition prior to curing. If anisotropy is wanted in the final product, it is recommendable to stretch after or during the curing. After curing the product consists of a threedimensional network, but can be stretched a little bit anyhow.

Preferably, the composition is stretched unaxially to a fiber with a thickness of less then 1 mm or biaxially to a sheet with a thickness of less then 1 mm.

If the curing of the acrylates is effected with supply of heat, the viscoelasticity of the semimanufacture will decrease and the semimanufacture may be subjected to elongation, which may be undesirable, due to the effect of gravity among other things. This can be corrected by having the curing take place in a bath filled with a liquid that is inert during the curing reaction and has a specific gravity which is virtually equal to that of the composition. It is possible to have the reaction take place under the influence of a catalyst, which is in the inert liquid and from there diffuses into the composition.

It is possible to postcure the products after they have been cured. This could render products with even better properties and especially with better high temperature properties.

Products made from a composition according to the invention are, depending on the starting materials, suitable for applications in those areas where a good temperature resistance, a good fire resistance and/or a good corrosion and solvent resistance are required besides good mechanical properties. -Examples are cable sheathing, fireproof clothing, asbestos replacement, high temperature filters, aircraft interiors, precursors for carbon fibre, food packagings (for instance for use in a microwave oven), condenser films, optical fibre and filament winding products. Here it is a significant advantage that, the acrylate resin compositions according to the invention need not be processed at a high temperature, in contrast to thermoplasts with a high intrinsic temperature resistance because these thermoplasts usually have a high weakening point. The invention is notably advantageous where sheets, films, fibres, tubes or other endless objects are required with one or more of the above-mentioned properties. The products, further, can be produced as bundles of thin filaments or as single, thicker monofilaments. The products according to the invention can be reduced to products of smaller length by cutting, sawing, breaking or similar methods.

The invention will be elucidated by means of the following examples and comparative experiments, without being restricted thereto.

Tensile tests on fibres were performed at room temperature on a Zwick tensile tester with fibre clamps. The initial length of the fibre was 50 cm; the crosshead speed was 5 cm/min. From the measured stress/strain curve the E-moduluε, the tensile strength and the elongation at break were determined.

As molecular weight the value according to the manufacturer was used. LOI measurements were performed according to ASTM D2863. DMA measurements were performed according to M.E. Brown, Introduction to Thermal Analysis, chapter 8, pp. 72 ff. TGA and DSC measurements were performed according to F.W. Billmeyer, Textbook of Polymer Science, John Wiley and Sons, ISBN 0 441 072966.

Experiments I- II Determination of the percentages of thermoplast required for spinnability

Polyethylene oxide (PEO) was obtained from Aldrich Chemie, W. Germany, with molecular weights of 200,000, 900,000 and 5,000,000 according to the manufacturer.

The epoxy acrylate resin was Ebecryl 600 R from 5. Radcure Specialties, Belgium.

Three PEO's of different molecular weight were suspended at room temperature in the epoxy acrylate resin with varying concentrations. The different molecular weights and concentrations are stated in tables 1 to 3. The PEO was 0 dissolved in the resin in a Brabender kneader at a temperature of 120°C.

The solution was transferred to dishes, which were subsequently heated to three different temperatures: 23°C in example I, 60°C in example II and 120°C in example III. 5 With a glass rod it was attempted to pick up a thread of material from each dish and then to wind the thread around a small spindle positioned horizontally over the dish. Then the spindle was put in a slow rotating motion so that the thread was continuously drawn from the solution 0 and wound around the spindle. By 'moderately spinnable' in the following tables is meant that only after several attempts and with very careful action was it possible to pick up such a thread from the solution, wind it around the spindle and rotate the spindle. 5

Table 1 Spinnability at 23°C

Exp. I Mol. weight Concentration of Spinnability

[g/mole] thermoplast [% w/w] a 200,000 1 + ⁰ b 5 + c 10 ++ d 20 ++ e 900,000 0.1 + f 1.1 + 5 g 2.5 ++ h 5.0 ++ i 10.0 ++ j 5,000,000 0.1 ++ k 0.2 ++ ' 0 .1 0.5 ++ m ■ 1.0 ++ The concentration of the thermoplast is given as weight percentage relative to the total composition. The spinnability was measured according to the test method as described above; — means very poorly spinnable, - means poorly spinnable, + means moderately spinnable, + means well spinnable and ++ means very well spinnable.

Table 2 Spinnability at 60°C

Exp. II Mol. weight Concentration of Spinnability

[g/mole] thermoplast [% w/w] a 200,000 1 b 5 c 10 + d 20 ++ e 900,000 0.1 f 1.1 g 2.5 + O h 5.0 + i 10.0 ++ j 5,000,000 0.1 + k 0.2 +

1 0.5 ++ 5 m 1.0 ++

For index see table 1.

Table 3 Spinnability at 120°C

Exp. ^'Ill Mol. weight . Concentration of Spinnability

5 [g/mole] thermoplast [ w/w] a 200,000 1 b 5 c 10 - d 20 +

+° e 900,000 0.1 f 1.1 g 2.5 h 5.0 i 10.0 ±

±μ j 5,000,000 0.1 + k 0.2 +

1 0.5 ++ m 1.0 ++

20 For index see table 1.

The tables show that of thermoplast with a higher molecular weight a lower percentage is required to make the solution spinnable than of thermoplast with a lower 25 molecular weight.

By comparing the tables with each other it can be seen that at higher processing temperatures relatively more has to be added to make the solution spinnable.

The invention relates by preference to a 30 composition with such a high percentage of thermoplast of a certain molecular weight that at the composition's processing temperature the composition is spinnable. This means that with a desired processing temperature of 23°C the composition contains at least 1% w/w of a thermoplast with a 35 molecular weight of 200,000.

With a desired processing temperature of 60°C the composition preferably contains 10% w/w of the thermoplast with a molecular weight of 200,000. • . -13-

With a desired processing temperature of 120°C the composition preferably contains 20% w/w of the thermoplast with a molecular weight of 200,000.

However, the quantities stated above apply here to PEO with the given acrylate. If other acrylate containing compositions and/or other HMW polymers are used, the figures will probably be different. The above guidelines provide a clear indication how the invention can be applied in analogous cases.

Comparative experiment A

The procedure of examples I to III was repeated, but without mixing in PEO in the epoxy acrylate. Again it was examined whether the solution could be spun to a fibre at a temperature of 23, 60 or 120°C. This was not the case.

Example IV The procedure of example II was repeated, polyvinyl acetate (PVA, Mowilith 70 from Hoechst Aktiengesellschaft, W. Germany) being suspended and dissolved in epoxy acrylate. The molecular weight of PVA was 1*10 and the concentration 15%. It was examined whether the solution could be spun to a fibre. This was the case.

Example V

The solution of example I was mixed with 3 wt.% UV initiator (Irganox 651 from Ciba-Geigy, France). The solution was transferred to a spinning vessel and spun at

100°C. Immediately upon spinning the spun fibre was cured by passing it under a UV lamp and then it was wound onto a rotating drum. Subsequently .the fibre was thermally aftercured at 160°C for 30 minutes. The fibre has an E-modulus of 2.4 GPa, a tensile strength of 60 MPa and an elongation at rupture of 5%.

Further, a DSC measurement with a heating-up rate of 10°C/min was performed on the solution containing UV initiator. It was found that thermal curing only started at 195°C. Further., it appeared that the solution hardly showed a curing reaction,^" if any, when heated to 175°C for 60 minutes. The maximum processing temperature of this mixture consequently is approximately 175°C before and during spinning.

Comparative experiment B

In the same way as in example V it was attempted to spin a fibre with epoxy acrylate, but with no PEO dissolved in it. This appeared to be impossible.

Example VI

With the solution of example V, containing 5 wt.% UV initiator, a slab was cast, which was UV cured for 3 minutes at 80°C and thermally aftercured for 30 minutes at 160°C. TGA measurements in oxygen and helium were performed on the material obtained, with a heating-up rate of

10°C/min. The weight loss appeared to be less than 1% at temperatures up to 350°C. An LOI measurement was performed on the material. The LOI was 26%. A DMA measurement was performed on the material. The Tg was 130°C.

Comparative experiment C

In the same way as in example VI, TGA_. measurements were performed on epoxy acrylate with UV initiator without PEO. The weight loss appeared to be less than 1% at temperatures up to 350°C. The LOI was 26%.

Example VII

An amount of epoxyacrylate (Ebecryl 600 , Radcure Specialties, Belgium) was mixed with an amount of urethaneacrylate (EW 89.9 of Radcure Specialties, Belgium; an oligomeric reaction product consisting of on average two _ hydroxyethylacrylates, two isoferondiisocyanates and one polypropyleneglycol• (n=17) ) , an amount of PEO (Aldrich Chemie, Germany; with MW=5xl0 ) and an amount of Darocure 1173^R (Merck, the Netherlands). The mixture was heated in an oven to 80°C and kept at this temperature during 12 hours. A homogeneous solution was obtained. The solution was transferred to a spinning vessel and spun at room temperature. Following spinning the fiber was cured under UV-light, under N₂-atmosphere, and wound on a spool. Of these fibers, the Young's modulus (E), the tensile strength (Ts) and elongation at break (eab) ware determined. The relative amounts and the results are given in table 4.

Table 4 Results of experiment VII

Experiment Vile was performed with spinning at 80°C. Composition Vile contained 15 g of Irgacure 651 instead of the Darocure 1173 .

From experiment VII can be concluded that these acrylates can be mixed in varying amounts, whereby different properties of the product can be obtained. This gives great freedom to act, which is an advantage.

Claims

1. Oligomeric acrylates containing composition suitable for the production of endless objects without the use of continuous carrier material, characterized in that the composition also contains a high molecular weight thermoplastic polymer.

2. Composition according to claim 1, characterized in that the thermoplast is dissolved in the acrylates.

3. Composition according to any one of the claims 1-2, characterized in that the composition contains, relative to the composition as a whole, 0.1 wt.% thermoplastic polymer with a molecular weight of more than 5,000,000 and up to about 50 wt.% of the thermoplastic polymer with a molecular weight of about 50,000.

4. Composition according to claim 3, characterized in that the composition contains, relative to the composition as a whole, at least 0.1 wt.% thermoplastic polymer with a molecular weight of more than 5,000,000 and up to at least 2.5 wt.% of the thermoplastic polymer with a molecular weight of 900,000.

5. Composition according to any one of the claims 1-4, characterized in that the oligomeric acrylates are chosen from the group comprising epoxy acrylates, hydroxy acrylates, carboxy acrylates and acrylamide copolymers.

6. Composition according to any one of the claims 1-5, characterized in that the thermoplast is chosen from the group comprising polyethylene oxide, polyamide, styrene maleic anhydride acrylonitrile copolymers, polypropeenoxide, polyvinyl alcohol polymethylmethacrylate and polyvinyl acetate.

7. Composition according to any one of the claims 1-6, characterized in that the composition contains fibrous strengthening material.

8. Process for making of an endless object without the use of continuous carrier material, characterized in that a composition according to any one of the claims 1-7 is heated to a suitable temperature, the thermoplast is at least partially dissolved, the composition is extruded or spun and subsequently at least partially cured.

9. Process according to claim 8, characterized in that the complete or partial curing of the oligomeric acrylates takes place in a bath filled with a liquid which is inert during the curing reaction and has a specific gravity which is virtually equal to that of the composition.

10. Process according to claim 9, characterized in that the inert liquid contains a catalyst which is suitable for the curing of oligomeric acrylates and can diffuse from the liquid into the composition.

11. Process according to claim 8, characterized in that the composition contains a UV initiator and is cured by exposing the composition to UV radiation.

12. Process according to any one of the claims 8-11, characterized in that the composition is stretched uniaxially or biaxially before, during or after the at least partial curing of the oligomeric acrylates.

13. Process according to claim 12, characterized in that the composition is uniaxially stretched to a fibre with a thickness of less than 1 mm.

14. Process according to claim 12, characterized in that the composition is stretched biaxially to a sheet with a thickness of less than 1 mm.

15. Process according to any one of the claims 8-14, characterized in that the composition is postcured.

16. Endless object obtained by at least partial curing of a composition according to any one of the claims 1-7 or by application of the process according to any one of the claims 8-15.

17.^' Composition as substantially described in the introduction of the specification and the examples.