JPS5841301B2 - Polyamide plastic parts - Google Patents

Description

[Detailed description of the invention] The present invention relates to polyamide resin compositions.

Specifically, the present invention relates to a foamable polyamide resin composition.

Conventionally, several proposals have been made regarding polyamide resin foams.

However, the foamable polyamide resin compositions used in ordinary molding machines have a low expansion ratio and poor reproducibility.
Further, it has the disadvantage that a foam having uniform and fine cells cannot be obtained.

As a result of intensive research aimed at improving the above-mentioned drawbacks of polyamide resin foam, the present inventors have found that the above-mentioned object can be achieved by containing a specific compound in addition to the polyamide resin and a blowing agent. They discovered this and arrived at the present invention.

The gist of the invention thus lies in a polyamide resin composition containing a polyamide resin, a blowing agent and a small amount of a polyincyanate compound.

The present invention will be explained in detail below.

As the polyamide resin used as a component of the composition of the present invention, for example, polyamides obtained by condensation polymerization of lactams having three or more membered rings, polymerizable ω-amino acids, salts of dibasic acids and diamines, etc. can be used.

Specifically, ε-caprolactam, aminocaproic acid,
Polymers of enantholactam, 7-aminohbutanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone; hexamethylenediamine, nonamethylenediamine, undecamethylenediamine,
Polymers obtained by polycondensing diamines such as dodecamethylene diamine and metaxylylene diamine with dicarboxylic acids such as terephthalic acid, inphthalic acid, adipic acid, cepatic acid, dodecane dibasic acid, and geltaric acid, or copolymers thereof. For example, nylon 6, nylon 7, nylon 6.6, nylon 12, nylon 6.10, nylon 6.11, nylon 6.I2, nylon 11, nylon 12, nylon 6T; or polymers or copolymers thereof. Mention may be made of all polyamide resins, including mixtures.

Among these polyamide resins, nylon 6,
Favorable results are obtained when using nylon 6.6 or copolymers thereof.

The polyamide resin used in the composition of the present invention preferably has a relative viscosity (measured in 98% sulfuric acid based on JIS K-6810) of 1.8 to 6, particularly 2 to 5.5.

If a polyamide resin with a relative viscosity (hereinafter abbreviated as ηrel) smaller than the above range is used, the strength of the resulting polyamide resin foam will decrease, and ηr
If a polyamide resin with a large el is used, it is not preferable because not only the moldability is inhibited but also the expansion ratio is not increased.

As the blowing agent used as a component of the composition of the present invention, at least one selected from azodicarboxylic acid amide, barium azodicarboxylate, and trihydrazinotriazine is preferably used.

The amount of the blowing agent added varies depending on the desired expansion ratio and the type of blowing agent, but is generally in the range of 0.5 to 10% by weight.

Regarding the foaming agent, as long as it has a decomposition temperature equal to or higher than the softening temperature of the polyamide resin, a foaming aid such as a decomposition accelerator or a decomposition inhibitor may be added as necessary.

Of course, the foaming aid may be selected as appropriate depending on the characteristics of the foaming agent.

The polyincyanate compound used as a component of the composition of the present invention is a compound having 2 or more incyanate groups in one molecule.

Usually aliphatic polyinsyanates or aromatic polyinsyanates are used.

Typical examples include tolylene diincyanate, hexamethylene diincyanate, methylene diphenyl diincyanate, O-xylene diincyanate, and II p ap manufactured by UP John, USA.
Polymethylene polyphenylinocyanate such as i@I+, tolylene diinocyanate) (7) A partially polymerized polyinocyanate compound, etc. can be used.

The amount of polyincyanate compound added is generally 0.1
A range of from 0.5 to 5% by weight is suitable, especially from 0.5 to 5% by weight.

If the amount of the polyincyanate compound is less than the above range, the foaming properties will not be sufficiently improved, and if the amount of the polyincyanate compound is greater than the above range, the foaming moldability will be impaired, which is not preferable.

The composition of the present invention can be produced using any conventionally known method.

Usually, it is manufactured by adding other components to the polyamide resin after polymerization.

Specifically, there are methods such as tri-blending each component immediately before molding, or adding one component to the polyamide resin in advance and then adding other components, but the method of tri-blending each component immediately before molding is It is also convenient and preferable.

In this triblending, it is preferable to first triblend the polyincyanate compound to the polyamide resin to moisten the surface, and then triblend the blowing agent, in order to achieve uniformity.

Of course, the composition of the present invention, even before polymerization of the polyamide resin,
Flame retardants, weather resistance improvers, stabilizers, mold release agents, heat resistant agents, antistatic agents, dyes,
It may be used in combination with additives such as colorants such as pigments, plasticizers, reinforcing agents, surfactants, fillers, lubricants, nucleating agents, or crosslinking agents.

Any method such as extrusion molding, injection molding, compression molding, or blow molding can be adopted as a method for heat molding the final product using the composition of the present invention, and the composition can be molded into the desired foam molded product such as a block, film, or sheet. be done.

The first feature of the present invention is that the foamed molded article obtained from the composition of the present invention has improved cell structure and the highest achievable expansion ratio, and is extremely stable.

In other words, as mentioned above, molded products based only on polyamide resin and a blowing agent are inferior in that the decomposed gas escapes to the outside of the system, the expansion ratio is unstable, or the molded product has large bubbles. Due to the polyincyanate compound, the composition of the present invention provides extremely stable molded articles.

Regarding the action of such a polyinocyanate compound, the polyamide resin probably undergoes crosslinking to some extent due to the interaction between the functional group of the polyinocyanate compound and the terminal group or amide bonding part of the polyamide resin, and as a result,
It is thought that the expansion ratio improves and the bubbles become finer by improving the gas trapping power generated by the blowing agent and by preventing the growth and aggregation of bubbles during the cooling process of the foamed molded product.

The second feature is that the composition of the present invention can be molded with a normal molding machine and does not require a molding machine exclusively for foaming, making it more versatile.

The third feature is that the foamed molded product obtained from the composition of the present invention has good strength.

That is, compared to ordinary foam molded products, it has superior physical properties such as bending strength and impact strength due to the miniaturization of the cells and the crosslinking of the polyamide resin by the polyinsyanate compound.

The details of the present invention will be specifically explained below based on Examples, but the present invention is not limited in any way by the Examples unless the gist of the invention is exceeded.

In the examples, ηrel (relative viscosity) is JIS K68
10, and stagnated in 98% sulfuric acid.

Example 1 and Comparative Example 1 Nylon 6 pellets with ηrel = 2.5 were treated with Upjohn (US) in an amount shown in Table 1 below based on the total composition.
Polymethylene polyphenylinocyanate "PAPI[F]" (manufactured by Up John) and a blowing agent were added and mixed, and the mixture was molded using a normal injection molding machine with a capacity of about 100 Y at a resin temperature of 240°C and a mold temperature of 40°C. 50×15
Molding was carried out using the limit amount that could maintain the shape in a mold having a thickness of 0x6.

The specific gravity and foaming state of the obtained foam were as shown in Table 1 below.

For comparison, when no polyincyanate compound was added, bis-
The results are also shown when using epoxy (manufactured by Shell Co., Ltd., bisphenol A-based epoxy compound, trademark, Epicote 1007) and when using an 80% aqueous solution of orthophosphoric acid and calcium carbonate as blowing agents.

Example 2 A foam was obtained in the same manner as in Example 1-1 except that nylon 6 pellets with ηrel = 3.5 were used.

The resulting foam had a specific gravity of about 0.38, and the cell size was uniform and fine, ranging from about 200 to 400 microns.

In addition, for comparison, when a foam was molded in the same manner as in Example 1 except that polymethylene polyphenylisocyanate was excluded, the specific gravity of the resulting foam was approximately 0.57, and the internal bubble distribution was nonuniform. -3% coarse bubbles were seen in various places.

Example 3 95.0% by weight of nylon 6 pellets with ηrel=3.5
and 2.0% by weight of polymethylene polyphenylinocyanate were added and mixed, and then 3% by weight of trihydrazino-8-)riazine was added and mixed, and the mixture was molded under the same molding conditions as in Example 1. The specific gravity of the obtained foam is approximately 0.4, and the size of the internal bubbles is 200 to 300μ.
It was extremely uniform.

For comparison, a mixture excluding the above incyanate was also molded under the same molding conditions, and the resulting foam had a specific gravity of approximately 0.52 and was non-uniform with bubbles of 400 to 1000 microns inside. Met.

Example 4 The compositions of Examples 2 and 3 were molded into a foam having a specific gravity of approximately 0.7 under the same molding conditions as described above, and the bending strength of the resulting foam was measured. The foams were found to be stronger than foams without polyincyanate compounds.

The table below shows the bending strength measurement results.

Claims (1)

[Claims] 1. A polyamide resin composition comprising a polyamide resin, at least one blowing agent selected from azodicarboxylic acid amide, barium azodicarboxylate, and trihydrazinotriazine, and a small amount of a polyincyanate compound.