JPS5858208B2 - Manufacturing method for crosslinked molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a crosslinked polyamide resin molded article.

Many attempts have been made to chemically crosslink thermoplastic polyamide resins to improve their physical, chemical, and mechanical properties.

However, since the thermoplastic polyamide resin has a high melting point or softening point, a crosslinking reaction occurs when the thermoplastic polyamide resin and the crosslinking agent are melted and kneaded, and stable kneading cannot be carried out. It has been considered almost impossible to subject a plastic polyamide resin composition to melt molding such as extrusion molding or injection molding.

Under these circumstances, in order to produce crosslinked thermoplastic polyamide resin molded products, additives that promote the crosslinking reaction of thermoplastic polyamide resin are melt-kneaded using ionizing radiation, ultraviolet light, etc., and the final product is melt-molded. The method involves crosslinking the molded product by irradiating it with radiation, ultraviolet rays, etc., copolymerizing polyamide with a polyfunctional monomer, melt-molding the final product using the polymer at a stage before the crosslinking reaction occurs, and then molding it into a solid phase. Methods such as crosslinking by reaction have been proposed, but all of them have drawbacks such as poor productivity and being uneconomical because they require equipment for ionizing radiation irradiation or solid-phase reaction.

Therefore, the present inventors investigated a method of obtaining a crosslinked thermoplastic polyamide resin molded product all at once without using the conventional complicated process. The present invention was achieved by discovering that a method of crosslinking at the same time as shaping is effective.

That is, the present invention uses a 10 mesh tyler (Ty 1
er) Mixing a thermoplastic polyamide resin powder that passes through a sieve and a crosslinking agent, then pressurizing and shaping the mixture while heating it to a temperature above the melting point or softening point of the thermoplastic polyamide resin and below the decomposition temperature, The present invention provides a method for producing a crosslinked molded article by reacting a crosslinking agent with a thermoplastic polyamide resin.

The thermoplastic polyamide resins used in the present invention include nylon 6, nylon 66, nylon 6101, nylon 6
Examples include aliphatic polyamides such as 12, nylon 11 and nylon 12, aromatic polyamides such as polyhexamethylene isophthalamide and polyhexamethylene terephthalamide, and mixtures or mutual copolymers thereof.

These thermoplastic polyamide resins are used in powder form, but in order to improve the appearance uniformity and degree of crosslinking of molded products, the upper limit of the particle size of the powder is extremely important, and the upper limit of the particle size of the powder is extremely important. This is essential.

When using polyamide resin powder with a large particle size that does not pass through a 10-mesh Ty-Ier sieve, not only will a uniform crosslinked product not be obtained, resulting in poor appearance, but also the degree of crosslinking of the molded product will be low. Undesirable.

There is no particular restriction on the lower limit of the particle size, and the smaller the particle size, the more preferable it is. However, the finer the grinding, the higher the grinding cost. Just choose an appropriate particle size.

In addition, if the particle size is in a range that passes through a 10-mesh Tyler sieve, the resin powder is further classified.
It is preferable to use the particles with a uniform particle size.

The Tyler sieve is a standard metal sieve sold by Tyler Co. in the United States, and the larger the mesh number, the more capable it is of passing powder with a small particle size. .

However, in the present invention, the 10-mesh tyler (Tyl)
er) Full ray means that the opening of the full ray mesh is between 1.651, and 10 mesh passes means the particle size of the powder that passes through the sieve mesh.

The crosslinking agent used in the present invention is one that can cause a crosslinking reaction with the thermoplastic polyamide resin at a temperature higher than the melting point or softening point of the thermoplastic polyamide resin, such as polyisocyanate, ethylene oxide, ethyleneimine, glyoxal, polyfunctional Epoxides, epichlorohydrin, etc. may be used, and among them, polyfunctional epoxides are preferred from the viewpoint of reactivity, physical properties of crosslinked products, and ease of handling.

For mixing the thermoplastic polyamide resin powder and the crosslinking agent, conventionally known mixing methods such as a type blender, Henschel mixer, roll mixing, etc. can be used.

The amount of crosslinking agent varies depending on the number of functional groups in the crosslinking agent and the degree of crosslinking required for the molded product, but it is usually in the range of about 0.1 to 10% by weight based on the thermoplastic polyamide resin. .

Depending on the type of crosslinking agent, it is also possible to heat the mixture within a range that does not cause a crosslinking reaction or to replace the atmosphere surrounding the mixture with an inert gas.

It is also possible to dissolve the crosslinking agent in a solvent, mix it with the thermoplastic polyamide resin powder, and then remove only the solvent.

In the present invention, various additives for further improving the properties of the thermoplastic polyamide resin during this mixing,
For example, fibrous reinforcing agents, fillers, lubricants, mold release agents, heat resistant agents,
Weathering agents, flame retardants, ultraviolet absorbers, coloring agents such as dyes and pigments, antistatic agents, and the like can be blended.

In particular, if a fibrous reinforcing agent such as glass fiber or carbon fiber is mixed in this step, it is advantageous because the fibers can be blended while maintaining relatively the fiber length without breaking the fibers.

The mixture of the thermoplastic polyamide resin powder and the crosslinking agent obtained by the above method is then heated and pressed to produce a crosslinked molded product. It is necessary to keep the temperature above the melting point or softening point and below the decomposition temperature.

If the heating temperature is below the melting point or softening point, not only the crosslinking reaction will not occur sufficiently, but also the degree of crosslinking will be poor in uniformity, which is not preferable.

Compression molding using a normal mated metal die can be favorably used as a heating and pressurizing method.

In addition, if the molded product is a plate-like object such as a sheet or film,
In addition to ordinary compression molding, it is also possible to adopt a method in which the mixture is supplied between a pair of endless metal belts, heated and compressed to continuously form a crosslinked plate-like body.

Thus, according to the present invention, it is possible to simultaneously achieve crosslinking and molding of thermoplastic polyamide resin, which was difficult with conventional methods, and to produce crosslinked polyamide resin molded products having a desired degree of crosslinking and good appearance etc. with high productivity. It becomes possible to manufacture it well.

The present invention will be described in detail below with reference to examples. In the examples, η means 1.0% polyamide dissolved in 98% sulfuric acid,
It represents the relative viscosity measured at 25°C.

The degree of crosslinking is 8.
After 48 hours of immersion in 8% formic acid at room temperature, the weight of formic acid insoluble matter was determined, and the value is expressed as a percentage of the weight before immersion in formic acid.

The particle size of the polyamide resin powder is determined by Tyler
) Expressed by the mesh number of the sieve when classified by the sieve.

Example 1 Nylon 6 chips with η = 2.7 were cryogenically ground and classified using a sieve to obtain 100 mesh pass nylon 6 powder.

1 epicoat to this powder” 819 (manufactured by 5hell Chemical)
A predetermined amount of was added and mixed using a Henschel mixer.

This mixed powder was supplied to a flat mold placed on a heating press set at 260°C, and without being pressurized, it was shaped into a 5 mu t sheet. After being left for 10 minutes, the flat mold was cooled to room temperature. It was transferred to a cooling press with water circulation and cooled.

During cooling, pressure was applied so that the thickness of the sheet became 5 mm.

Table 1 shows the results of examining the appearance and degree of crosslinking of this molded product.

It can be seen that by the above method, a molded article with a high degree of crosslinking and an excellent surface appearance can be obtained.

On the other hand, an attempt was made to make an S-shaped sheet by extrusion molding nylon 6 powder to which the same amount of "Epicoat" 819 was added as in the above actual case, but it was difficult to extrude stably even when 1.5 parts of "Epicoat" 819 was added. However, due to the surface roughening of the sheet, a significantly smooth molded product could not be obtained.

Further, when the amount was 3 parts or more, extrusion molding was impossible at all.

Example 2 Nylon 6 powder pulverized in the same manner as in Example 1 was classified using a Tyler sieve to the intensities shown in Table 2 to prepare nylon 6 powders having various particle sizes.

5% by weight of "Epicote" 817 was added to each of these powders and mixed using a Henschel mixer.

Next, a sheet with a thickness of 3 mm was formed using this powder mixture in the same manner as in the examples, and the appearance and degree of crosslinking of the obtained sheet were evaluated.

These results are shown in Table 2.

As is clear from the results in Table 2, excellent crosslinked molded products can be obtained by using nylon 6 powder having a particle size of 10 mesh passes, and 20 mesh passes are especially necessary to obtain molded products with a high degree of crosslinking of 30% or more. powder is preferred.

Further, even if a powder that does not pass 10 meshes is used, no crosslinking occurs at all, and only molded products with poor appearance are obtained.

Example 3 3% by weight of ``Epicoat'' 819 was added to a powder of nylon 66 having a particle diameter of 100 mesh or less and having η = 3.10 using a Henschel mixer.

A mantid metal die (bottom 70φ, height 30, diameter 80φ) was attached to a heating press set at 285℃ with this powder.
, a cup-forming mold with a wall thickness of 1.0 MAIL t), pressurized and shaped, and held for 3 minutes.Then, the heater of the hot press was turned off while the pressure was maintained, and cooled.

A molded article with a degree of crosslinking of 71% and an extremely good appearance was obtained.

Molding a molded product with the same degree of crosslinking by injection molding
This was completely impossible as the polymer did not flow inside the cylinder.

Claims (1)

[Claims] A thermoplastic polyamide resin powder that passes through a 110-mesh Tyler sieve is mixed with a crosslinking agent, and then this mixture is heated to a temperature above the melting point or softening point and below the decomposition temperature of the thermoplastic polyamide resin while applying pressure. A method for producing a crosslinked molded article, which comprises reacting a crosslinking agent and a thermoplastic polyamide resin at the same time as shaping.