WO2013056705A1

WO2013056705A1 - Process for producing objects from irradiation cross-linked polyamide

Info

Publication number: WO2013056705A1
Application number: PCT/DE2012/100325
Authority: WO
Inventors: Michel Gschwendtner; Franziska WEICHELT
Original assignee: Minervius Gmbh; Hülsmann, Ralf
Priority date: 2011-10-20
Filing date: 2012-10-19
Publication date: 2013-04-25
Also published as: DE102011054629A1

Abstract

The invention relates to a process for producing objects from irradiation cross-linked polyamide, comprising the following method steps according to their chronological order: a) irradiation cross-linking of a polyamide raw material in solid form; b) shaping the irradiation cross-linked polyamide raw material to form an end product.

Description

Process for the preparation of articles of radiation crosslinked

polyamide

DESCRIPTION

The invention relates to a process for the production of articles from radiation-crosslinked polyamide.

Radiation crosslinking (hereinafter also referred to as irradiation) is understood here as meaning a generally known process for modifying polymers with the aid of ionizing radiation.

EP 1 966 280 A1, US 2008/0207782 A1 and US Pat. No. 4,444,816 each describe processes for radiation cross-linking of polyamides. However, in the above-mentioned methods, the radiation crosslinking takes place in each case after the object to be produced has already been formed from a raw material. The result of this is that the process of radiation crosslinking has to be matched to the respective geometry of the object, which makes the process technically complex.

The invention has for its object to provide a process engineering easy to be performed method for the production of articles of irradiated polyamide.

This object is solved by the features of patent claim 1. Advantageous embodiments are described in the subclaims.

According to the invention, the process for the production of articles made of radiation-crosslinked polyamide has the following process steps, which are listed in chronological order: a) Radiation crosslinking of a polyamide In the solid state, and b) transforming the radiation-crosslinked polyamide raw material into a final product.

In other words, irradiation of the polyamide takes place before

Shaping, i. Polyamide raw materials are ionized with

Radiation treated while branched / partially crosslinked, the

Raw materials e.g. in the form of granules, pellets, flakes, beads or powders can be used. Subsequently, the shaping takes place, i. the transformation of the cross-linked raw material into the desired

End products (objects).

Due to the radiation crosslinking of the raw material, it is not necessary, the

Adjust parameters of the networking process to the concrete object to be produced. The process parameters are rather

regardless of the desired end product. This leads to a

procedural simplification of the process.

By polyamide are meant polymers whose repeating units possess the amide group as a characteristic feature. This includes both homopolyamides and copolyamides. Under

Homopolyamides are understood to mean polyamides which can be described by a single repeating unit. Copolyamides are understood to mean polyamides which can be described by different repeating units. Furthermore, the term polyamides also includes polyamide blends, i. blends of various types of polyamides (e.g., PA6 / PA66 blends) as well as blends of polyamide and others

Polymers (e.g., polystyrene / polyamide blends or acrylonitrile-butadiene-styrene (ABS) / polyamide blends).

Preferably, the radiation crosslinking takes place in the presence of a crosslinking additive. The crosslinking additive may be solid, liquid or be gaseous and contains at least one multiple bond. In the case of solid or liquid crosslinking additives, they must be introduced into the polyamide raw material before the irradiation by melt mixing / compounding. Examples of particularly suitable solid / liquid crosslinking additives are triallyl cyanurate or triallyl isocyanurate. The crosslinking additive can be used in concentrations of 0.01 - 20%. The irradiation can be in the presence of oxygen

(Ambient atmosphere) or in an inert gas atmosphere (e.g., nitrogen). By irradiation in ambient atmosphere, the

Reacting polyamides via a peroxide radical mechanism with oxygen molecules from the air to form new polar functional groups (e.g.

Carboxyl or carbonyl groups) in the polyamide, this is commonly called oxidation. The radiation-induced oxidation can increase the compatibility of polyamides over other materials (such as

Fillers) and improve the adhesion of polyamides to polar materials (such as metal surfaces). By irradiation in one

Inert gas atmosphere, i. in the absence of oxygen, the formation of polar functional groups is largely prevented. The gaseous crosslinking additive can be added directly during the irradiation, during the irradiation diffuse into the polyamide and crosslink there with the polyamide. This method is preferable because an additional compounding step of polyamide and crosslinking additive is omitted here and the associated disadvantages, e.g. Chain degradation of the polyamide during compounding, be reduced. Examples of gaseous

Crosslinking additives are ethylene or acetylene.

Radiation crosslinking occurs at a temperature at which the polyamide raw material is in the solid phase (ie, solid state). In particular, the starting polymer may be in the form of granules, pellets, flakes, spheres or powders. Preferably, the radiation crosslinking takes place under ambient pressure. In a particularly advantageous embodiment, the irradiation takes place at a temperature below the crystalline melting temperature of the

Polyamide raw material. In this procedure, the amorphous regions are preferably branched / partially crosslinked, while the crystalline regions remain largely unchanged. In this way, the processability of the crosslinked polyamide is largely retained.

Irradiation is by means of ionizing radiation, i. possible

Irradiation sources are in particular electron radiation, gamma radiation or X-radiation, but preferably electron radiation. The irradiation dose should be between 0.1 and 500 kGy, preferably in the range of 1 to 60 kGy; the choice of irradiation dose depends on the type of polyamide, the additive content and / or the desired degree of crosslinking.

In a further preferred embodiment, the polyamide raw material is crosslinked to a gel content of 0.01 to 10%. This preferred degree of crosslinking is well below the usual degrees of crosslinking (gel content 60-70%) and allows a simple and simple further processing / transformation of the irradiated polyamide.

If the radiation treatment of the polyamide raw material with the above-mentioned relatively low irradiation doses (up to 60 kGy), is in the

Polyamide obtained only the above-mentioned low degree of crosslinking (gel content of 0.01 -10%), so that the material also after the

Radiation modification remains processable and recyclable and from it

End products can be molded. In contrast, products that have been chemically crosslinked or radiation-crosslinked after shaping are no longer deformable or recyclable. A reshaping of the irradiated polyamide can in particular by an extrusion process or a

Injection molding process done.

Exemplary embodiments Example 1

500 g polyamide granules PA6.10 or PA6 are packed in a gas-impermeable bag. After vacuuming, the bags are filled with ethylene gas until the external and internal pressures are equalized.

The samples are irradiated in a gamma-irradiation facility at a dose of 8.0 kGy, then annealed at 80 ° C for 8 hours and finally cooled to room temperature. During the annealing process, generally, the long lived polyamide radicals formed during irradiation may continue to react with the crosslinking additive. The tempering process changes the color of PA6.10 granules from colorless to slightly pink, to PA6 or from colorless to slightly yellow. The mechanical and theological properties of the modified PA6.10 are compared with those of the untreated PA6.10. Significant increase in complex viscosity due to branching reactions after radiation modification can be observed. It has also been shown that the spray pressure with which the tensile bars are produced for the investigation of the mechanical properties is only slightly increased by the radiation modification, ie that the modified polyamides, without having to make any changes to the machine, become a final product (tensile bars) ) can be further processed. By radiation modification, an increase of the tensile strength and the modulus of elasticity can be achieved. Example 2:

500 g partially aromatic polyamide granules PA6.6T are packed in a gas-impermeable bag. After vacuuming the bag is filled with ethylene gas until the external and internal pressure are equalized.

The sample is irradiated in a gamma irradiation facility at a dose of 16 kGy, then annealed at 80 ° C for 8 hours and finally cooled to room temperature. During annealing, a color change from colorless to pink can be detected. The mechanical and theological properties of the modified PA6.6T are compared with those of the untreated PA6.6T. There may be a slight increase in complex viscosity due to branching / crosslinking after radiation modification. The injection pressure with which the tension rods are produced for the investigation of the mechanical properties does not change almost as a result of the radiation modification, i. The modified PA6.6T can be processed into a final product (tension rods) without having to make any changes to the machine. By radiation modification, a slight increase in tensile strength and a reduction in elongation at break can be observed.

Example 3:

First, in a laboratory extruder, a compound of 1 wt .-% Tnallylisocyanurat prepared in polyamide PA6.6, extruded into a water bath and then cut into pellets (granulated). After drying, the pellets are irradiated with high energy electrons from an electron beam accelerator (10 MeV) at ambient pressure and in ambient atmosphere at a surface dose of 4, 16 and 24 kGy, respectively. The mechanical and thermal properties of the modified PA6.6 are compared with those of the untreated polyamide PA6.6 compared and it can be found an improvement of the mechanical and thermal properties.

Example 4:

First, in a laboratory extruder, a compound of 1% by weight of triallyl cyanurate in polyamide PA12 is prepared, extruded into a water bath and then cut into pellets (granulated). After drying, about 500 g of the granules are each packed in a gas-impermeable bag. After vacuuming, the bags are filled with an inert gas (nitrogen) until the external and internal pressures are equalized. The samples are irradiated with high-energy electrons from an electron irradiation facility (10 MeV) at room temperature with a surface dose of 4, 16 or 24 kGy. Subsequently, a part of the samples is annealed at 80 ° C for 8 hours, the other part is not annealed. The mechanical and thermal properties of the modified polyamides are compared with those of the untreated polyamide PA12 and an improvement in the mechanical and thermal properties can be observed.

Claims

1 . Process for the production of articles made of irradiated polyamide with the following process steps given in chronological order:

a) Radiation crosslinking of a polyamide raw material in the solid state;

b) forming the radiation crosslinked polyamide raw material into a final product.

2. The method of claim 1, wherein the method step a) in

Presence of a crosslinking additive takes place.

3. The method according to any one of the preceding claims, wherein the

Radiation crosslinking takes place at a temperature which is below the crystalline melting temperature of the polyamide raw material.

4. The method according to any one of the preceding claims, wherein the method step b) by an extrusion process or a

Injection molding process takes place.

5. The method according to any one of the preceding claims, wherein the

Radiation crosslinking takes place until the polymide raw material has a gel content of 0.01 -10%.

6. The method according to any one of the preceding claims, wherein the

Radiation crosslinking with an irradiation dose of 0.1-500 kGy takes place. Method according to one of the preceding claims, wherein the polyamide raw material is present as granules or powder.

Method according to one of the preceding claims, wherein the method step a) at room temperature and under

Ambient atmosphere is performed.