JPS584738B2 - 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 polyamide resin composition with improved flexibility at low temperatures.

Polyamide resins have good gas barrier properties against oxygen and the like, so they are widely used as films for frozen foods.

However, polyamide resin films sometimes develop pinholes at low temperatures, impairing their gas barrier properties, and there has been a need for polyamide resin films with improved flexibility at low temperatures.

In response to this, attempts have been made to add sulfonamide plasticizers to polyamide resins, but these have had various drawbacks.

In view of the above-mentioned circumstances, the present inventors conducted extensive research and found that the objective could be achieved by adding a specific compound to a polyamide resin, thereby achieving the present invention.

That is, the gist of the present invention resides in a polyamide resin composition characterized by containing a polyamide resin and a small amount of a tetrahydric or higher polyhydric alcohol having 4 to 12 carbon atoms.

The present invention will be explained in detail below.

Various well-known polyamide resins can be 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 acid diamines, etc. can be used.

Specifically, epsilon-cab lactam, aminocaproic acid,
Polymers of enantholactam, 7-aminehebutanoic acid, 11-amineundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone, etc.: hexamethylenediamine, nonamethylenediamine, undecamethylenediamine,
Polymers obtained by polycondensing diamines such as dodecamethylene diamine and metaxylene diamine with dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, dodecane dibasic acid, and glutaric acid, or copolymers thereof, e.g. , nylon 6, nylon 7, nylon 6,6, nylon 6,10, nylon 6.11, nylon 6,12A, nylon 11, nylon 12, nylon 6T; or mixtures of these polymers or copolymers. Examples include resins.

Commonly used polyamide resins include homopolyamides such as nylon 6, nylon 11, and nylon 12, nylon 6,6, nylon 6/6,
6, nylon 6,10, nylon 6,12, nylon 6
Examples include copolyamides such as /6 and 6/12.

In particular, the best results are obtained when nylon 6/6,6 copolymer is used.

Of course, these polyamide resins may be blended with small amounts of other resins.

In addition to the polyamide resin, the composition of the present invention needs to contain a polyhydric alcohol having 4 to 12 carbon atoms and having a valence of 4 or more (hereinafter abbreviated as "polyalcohol").

Examples of such polyalcohols include tetrahydroxybutane such as erythritol, xylitol,
Pentahydroxypenkune such as arabitol, hexahydroxyhexane such as sorbitol, mannitol, galaxitol, and inositol, hexahydroxyhexane such as 1-hydroxymethyl sorbyl, and octahydroxyoctane have the same number of carbon atoms in the molecule. Polyalcohols having hydroxyl groups, 1,2,3.78-pentahydroxyoctane, 1,2,3,4,7,8-hexahydroxyoctane, 1,2,3,6,7,11,
Polyalcohols such as 12-hepetahydroxydodecane can also be used.

When these polyalcohols have optical isomers, any of the D-unit, L-unit and racemic forms can be used.

Among these polyalcohols, polyalcohols having the same number of hydroxyl groups as the number of carbon atoms in the molecule are used, preferably polyalcohols with 4 to 8 carbon atoms, especially 6 carbon atoms, are suitable for food use. It is also preferable.

The polyalcohol used in the present invention is preferably of A high purity.

In particular, it is desirable that the moisture content be low, and the moisture content should be 1
It is preferable that the amount is less than % by weight.

Usually, it is preferable to use a powdered polyalcohol.

The content of polyalcohol in the composition of the present invention is usually 1 to 1.
10% by weight, preferably 2-7.5% by weight.

If the amount of polyalcohol is less than the above range, the desired effect will not be achieved, and if it is more than the above range, foaming may occur during molding, which is not preferable.

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

Usually, it is preferable to add polyalcohol to the polyamide resin after polymerization.

Specifically, for example, polyamide resin chimps or powder are simply mixed with polyalcohol using a tumbler or high-speed fluid mixer, and the mixture is heated and molded, or polyamide resin chips containing a large amount of polyalcohol in advance are produced. Alternatively, the powder may be diluted with polyamide resin chips or powder that does not contain polyalcohol to obtain the desired content, and then heated and molded.

Any method such as extrusion molding, injection molding, compression molding, blow molding, etc. can be used as a method for thermoforming the composition of the present invention, and the composition can be molded into various molded products such as films, sheets, blocks, pipes, filaments, and the like.

Of course, the composition of the present invention may further contain a flame retardant, a mold release agent, a weather resistance improver, a stabilizer, a heat resistant agent, and an antistatic agent at any stage from before polymerization of the polyamide resin to molding of the final product. It may be used in combination with additives such as colorants such as dyes and pigments, plasticizers, reinforcing materials, surfactants, inorganic fillers, lubricants, nucleating agents, or crosslinking agents, and polytetrafluoroethylene, polyester. , polymers such as ABS resins can also be added.

The present invention has been described in detail above, and the polyamide resin molded product obtained using the composition of the present invention has the following features compared to conventional products.

First of all, the molded articles obtained from the compositions according to the invention have sufficient flexibility even at low temperatures.

Second, the composition of the present invention does not emit smoke during heat molding and does not worsen the working environment.

Third, the present invention requires only a small amount of additives.

Fourthly, thin-walled molded products such as films and sheets obtained from the composition of the present invention are less likely to generate pinholes even at low temperatures.

The present invention will be specifically explained with reference to Examples below.
The present invention is not limited in any way by the following examples unless the gist of the invention is exceeded.

In the examples, "parts" means "parts by weight" and "%" means "% by weight" unless otherwise specified.

Moreover, the tensile test was conducted according to JIS-K-6781.

Examples and Comparative Examples Nylon 6/6,6 copolymer (composition molar ratio 6/6, 6=85/15) chip ("NOVAMID2" manufactured by Mitsubishi Chemical Corporation)
030" grade) and 5 parts of sorbitol "Sorvit-D" (manufactured by Shin Nihon Rika Co., Ltd.) were blended in a tumbler, and 25 parts
A film of mμ was formed.

This film was subjected to a tensile test under two conditions: (1) 23° C., 65% relative humidity and (2) 5° C., 50% relative humidity.

The results are shown in Table-1. In addition, as comparative examples, films were formed in the same manner as above for those that expanded without adding sorbitol and those that replaced sorbitol with ethyl toluenesulfonamide, a plasticizer for polyamide resin.
We conducted a test.

The results are shown in Table-1.

These results show that the composition of the present invention has higher breaking strength and elongation at low temperature and low humidity and lower tensile modulus than the polyamide resin itself, that is, flexibility is imparted to the polyamide resin. It can be seen that the tensile modulus of the polyamide resin is large at low temperature and low humidity, indicating that the polyamide resin is brittle.

In addition, in the case of Comparative Example 2, heavy smoke was generated during film formation.

Claims (1)

[Claims] 1. A polyamide resin composition characterized by containing a polyamide resin and a small amount of a polyhydric alcohol having 4 to 12 carbon atoms and having a valence of 4 or more.