JPH04159363A - Thermoplastic resin composition for refrigerant hose - Google Patents

Abstract

PURPOSE:To prepare the title compsn. excellent in resistance to refrigerant permeation and flexibility by compounding the main component comprising a polyamide resin and an elastomer having an anionic polar group with a specific cross-linker and a specific cross-linking aid, and subjecting the resulting compsn. to cross-linking reaction. CONSTITUTION:A main component comprising 45-80wt.% polyamide resin and 20-55wt.% elastomer having an anionic polar group is compounded with a cross- linker (e.g. magnesium oxide or lead oxide) and a cross-linking aid comprising a fatty acid (e.g. stearic acid or palmitic acid) each in a specified amt., and subjected to cross-linking reaction to give the title compsn., which is excellent in heat resistance, etc., as well as in flexibility and resistance to refrigerant permeation, is suitable for a refrigerant hose used in an automotive cooler or air conditioner, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The invention of the second application particularly relates to a thermoplastic resin composition for a refrigerant hose that is excellent in refrigerant permeation resistance and flexibility.

[Conventional technology]

Materials for refrigerant hoses used in automobile coolers, air conditioners, etc. are required to have refrigerant permeability, flexibility, heat resistance, and low-temperature impact resistance.

Conventionally, nylon 11 was used as a material for this type of refrigerant hose.
Research has been conducted on a method of blending a plasticizer to give flexibility while taking advantage of the excellent refrigerant permeation resistance of polyamide resins such as nylon 6766 and nylon 6766, but this method has the following problems. .

That is, elution of the plasticizer over time, loss of flexibility due to scattering of the plasticizer in a high temperature atmosphere, etc.

Therefore, in order to solve this problem, a method of dispersing an elastomer in a polyamide resin and crosslinking it is being developed.

However, when using the above method, although other properties such as heat resistance can be satisfied, it is extremely difficult to achieve both the excellent refrigerant permeation resistance that polyamide resin has and the flexibility that elastomer inherently has. It was not possible to provide something that had both.

[Problem to be solved by the invention]

Therefore, the invention of this application is to create a thermoplastic resin composition that has both excellent refrigerant permeation resistance and flexibility, which are required as well as other properties for materials for refrigerant hoses used in automobile coolers, air conditioners, etc. The challenge is to provide things.

(Means for Solving the Problem) In order to solve the above problem, in the invention according to claim 1 of this application, A, a polyamide resin of 45 to 80% by weight, B, an elastomer having an anionic polar group of 20 to 80% by weight. 55% by weight as a main component, a predetermined amount of fatty acid as a C6 crosslinking aid, D, a predetermined amount of a crosslinking agent, and a crosslinking reaction.

The polyamide resin used in the invention of this application is
A thermoplastic resin with an amide bond -C○-NH- in the main chain, including nylon 6, nylon 12, and nylon 6.6.
, Nylon 11, Nylon 6.9, Nylon O: /6,10
, Nylon 76/66, Nylon 66/610, etc., and preferably Nylon 6, which has particularly excellent gas barrier properties and is inexpensive, but is not limited to these.

Examples of the elastomer used in the invention of this application include ethylene-propylene copolymer, nitrile rubber, and acrylic rubber.

Further, as the anionic polar group of the elastomer used in the invention of this application, a carboxyl group, an acid anhydride group, an epoxy group, a sulfone group, etc. can be used, and a carboxyl group is preferably used. Yes, but not limited to these.

As described above, assuming that the elastomer has anionic polarity M, this polar group promotes compatibilization of the polyamide resin and the elastomer, so that the thermoplastic resin composition is considered to have a microdispersed structure.

The aforementioned self-anionic polar group may be present in the elastomer as a block copolymer or a graft copolymer.

Examples of the crosslinking aid used in the present invention include fatty acids, which are effective as molding aids.

Examples of the fatty acid include stearic acid, barmitic acid, oleic acid, myristic acid, etc., and preferably stearic acid and barmitic acid can be used, but the fatty acid is not limited to these.

If only the polyamide resin and elastomer are blended without adding a fatty acid as a crosslinking aid, a rapid reaction occurs between the cationic polar groups of the polyamide resin and the anionic polar groups of the elastomer, making stable molding impossible.

In particular, when the polyamide resin is about 70% by weight and the elastomer is about 30% by weight, the reaction between the two reaches its peak and gelation becomes significant, making molding using an extruder, for example, completely difficult.

Also, contrary to the above example, if the blending ratio of polyamide resin and elastomer is elastomer-rich, the load on the extruder etc. is relatively small, and the extrusion may look good. The elastomer is extruded while enveloping the gel produced by the rapid reaction between the two, and the resulting resin composition has an extremely poor dispersion state.

However, when fatty acids are added to these as crosslinking aids,
It has been found that rapid reactions between the polar groups of the polyamide resin and the elastomer can be suppressed, and a highly dispersed state can be obtained.

This is possible by adding a crosslinking aid to the thermoplastic resin composition, whether the elastomer is dispersed in the polyamide resin or the polyamide resin is dispersed in the continuous phase of the elastomer. This is thought to be due to good microdispersion.

Here, as an embodiment of adding the crosslinking aid, there are the following methods. The first embodiment is a method in which the polyamide resin, elastomer, and crosslinking aid are added almost simultaneously.

The second embodiment is a method in which a crosslinking aid is added after the gelation of the polyamide resin and elastomer has progressed to a certain level, and the third embodiment is a method in which a crosslinking aid is added to a polyamide resin and an elastomer This is a method in which a crosslinking agent is added to a crosslinking agent, and these are separately prepared, and both are reacted.

Molding is possible using any of the three methods described above.

As the crosslinking agent, metal oxides and amines can be used, and metal oxides such as magnesium oxide and lead oxide can be preferably used, but the crosslinking agent is not limited to these.

When a crosslinking agent is added, the elastomer is crosslinked to increase its viscosity, resulting in a structure in which elastomer fine particles are microdispersed in the polyamide resin.

In addition, the proportion of the polyamide resin exceeds about 80% by weight and the proportion of the elastomer exceeds about 2% by weight with respect to the thermoplastic resin composition.
When it is less than 0% by weight, it has excellent refrigerant permeation resistance but lacks flexibility. On the other hand, if the proportion of polyamide resin is less than about 40% by weight and the proportion of elastomer exceeds about 60% by weight, the flexibility will be excellent, but the refrigerant permeation resistance will be significantly reduced.

The above molding can be carried out continuously using a batch mixer or an extruder; It is possible to stably produce thermoplastic compositions.

This means that even though the dispersed elastomer particle size could not be reduced beyond a certain level in a batch mixer due to repeated dispersion and recombination, continuous molding using an extruder hardly causes recombination, making it possible to achieve even more microdispersion. It seems to be from.

The thermoplastic composition molded using an extruder had better refrigerant permeation resistance than that molded using a hatch-type kneader.

In addition, known fillers, antioxidants, ultraviolet absorbers, etc. as additives for rubber may be added as necessary.

[Examples] The invention of this application will be described below based on Examples and Comparative Examples.
This will be explained in more detail.

The thermoplastic resin compositions described in Examples 1 to 7 and Comparative Examples 1 to 4 shown below were molded using the formulations shown in Table 1 by the following method.

[Example] As shown in Table 1, the polyamide resin was nylon 6 (1022B manufactured by Ube Industries) or nylon 6/66 (manufactured by Ube Industries, Ube Nylon 501).
3B), ethylene-acrylic copolymer rubber (VAMAC-G manufactured by Showa Denko/Dupont ■) as an elastomer, stearic acid as a fatty acid as a crosslinking aid, MgO as a metal oxide as a crosslinking agent, and MgO as an anti-aging side. Amine-based non-contaminating Tsukrank CD (manufactured by Iriuchi Shinko ■) was used.

(Example 1) A twin-screw extruder (RAIYUKAI TEM-30B) was set at a temperature close to the melting point of the polyamide resin, and the polyamide resin and elastomer were added at about 70% by weight and about 30% by weight, respectively, and further as a crosslinking aid. of fatty acids and the number of screw rotations is 10.
A thermoplastic resin composition was obtained by kneading with Or, p, -, adding a metal oxide as a crosslinking agent midway through extrusion molding to cause a crosslinking reaction.

Here, it is also possible to perform extrusion molding by kneading and melt-blending the polyamide resin, elastomer, and fatty acid, and then adding a crosslinking agent thereto to cause a crosslinking reaction.

(Examples 2 to 5) In the same manner as in Example 1, the polyamide resin and elastomer were used in Example 2 at approximately 65% by weight and approximately 35% by weight, respectively.
, about 60% by weight in Example 3 and about 40% by weight in Example 4.
In Example 5, about 55% by weight and about 45% by weight, and about 50% by weight in Example 5.
About 50% by weight, a crosslinking aid, and a crosslinking agent were added and extrusion molding was performed to obtain a thermoplastic resin composition.

(Example 6) A mixer (Rheomics 600 manufactured by Haake) was set at a temperature close to the melting point of the polyamide resin, and about 55% by weight and about 45% by weight of the polyamide resin and elastomer were charged, respectively.
While continuing kneading at a rotor rotation speed of 3 Or, p, m, fatty acid as a cross-linking agent, metal oxide as a cross-linking agent, and further anti-aging agent are added, and the kneading torque is displayed in real time to see if sufficient cross-linking has been achieved. After checking the value, I took it out.

(Example 7) In the same manner as in Example 1, extrusion molding was carried out by adding about 80% by weight and about 20% by weight of polyamide resin and elastomer, as well as a crosslinking aid and a crosslinking agent, to obtain a thermoplastic resin composition. I got something.

Next, a comparative example will be explained.

Comparative Examples 1 and 2 shown below are examples in which no crosslinking agent is used, Comparative Example 3 is an example in which the polyamide resin is approximately 40% by weight and elastomer is approximately 60% by weight, and Comparative Example 4 is an example in which the polyamide resin is approximately 60% by weight. An example is 90% by weight and about 10% by weight of elastomer.

(Comparative Example 1) A twin-screw extruder (Toshiba Machine TEM-30B) was set at a temperature close to the melting point of the polyamide resin, and the polyamide resin and elastomer were added at about 70% by weight and about 30% by weight, respectively, and as a crosslinking aid. Blend fatty acids and perform kneading and extrusion,
A melt blended resin was obtained.

The blended resin thus obtained was molded as a thermoplastic resin to obtain a sheet having a thickness of 1Ill111.

(Comparative Example 2) In the same manner as in Comparative Example 1, about 65% by weight and about 35% by weight of a polyamide resin and an elastomer, respectively, and a fatty acid as a crosslinking aid were blended and mixed wire extrusion was performed to obtain a melt-blended resin. Obtained.

(Comparative Example 3) A twin-screw extruder (Toshiba Machine t1TEM-30B) was set at a temperature close to the melting point of the polyamide resin, and the polyamide resin was used in an amount of about 40% by weight, the elastomer in an amount of about 60% by weight, and a crosslinking agent as a crosslinking aid. Add fatty acids and screw rotation speed 10 Or,
After kneading with p and m, a metal oxide was added as a crosslinking agent during the process, and extrusion molding was performed to accelerate the crosslinking reaction.

(Comparative Example 4) In the same manner as Comparative Example 3, polyamide resin and elastomer were blended at about 90% by weight and about 10% by weight1, respectively, and a fatty acid as a crosslinking agent, and a metal oxide was added as a crosslinking agent during the process. and extrusion molding.

(Reference) The elastomer alone was charged into a kneader (Rheomix 600 manufactured by Haake) heated to around 130°C, and crosslinking aids, crosslinking agents, fillers, and anti-aging agents were added, and the rotor rotation speed was 80 r, p. , s+.

After kneading, the mixture was press-molded and crosslinked at 180° C. for 30 minutes to obtain a crosslinked sheet of elastomer alone.

Using the muko-molded product as described above, a refrigerant permeability test, a tensile test, an oil resistance test,
High temperature weight loss rate measurement and heat aging test were conducted. The results are shown in Table 3.

In addition, as a measure of flexibility, the yield point strength was evaluated, or for those that did not show a yield point, the stress at 20% tension was evaluated.

As is clear from this table of results, the thermoplastic resin composition according to the present invention has both the excellent refrigerant permeation resistance of a polyamide resin and the flexibility of an elastomer.

or,. The graph in FIG. 1 shows the relationship between the content of elastomer in the thermoplastic resin composition and gas permeability, and the graph in FIG. 2 shows the relationship between gas permeability and flexibility.

(Hereinafter, blank space) Table 1 In Table IL, the total weight ratio of nylon and EAR is set as 100.

(Hereafter, margins) Table 1 (continued) [Hereafter, margins] Table 1 (continued) (Hereafter, margins) Table 1 (continued) Book 1 Ube Industries type Ube nylon l0IIFB*2 Showa Denko/DuPont Baymac G car 3 Large Manufactured by Koushinka Chemical Industry Tsukrank CD*4 Ube Industries type Ube Nylon 5013B (hereinafter, blank) Table 1 (continued) (hereinafter, blank) Table 1 (continued) (hereinafter, blank) Table 2 - Effect of the invention ] The thermoplastic resin composition for refrigerant hoses of the invention of this application is
As is clear from the results of the comparison between the above examples and comparative examples, it has excellent physical properties such as heat resistance, and has excellent flexibility and refrigerant permeation resistance as shown in the tensile test and refrigerant permeation resistance test. have a property. Therefore, it is very suitable as a material for refrigerant hoses used in automobile coolers, air conditioners, etc.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the freon gas permeability of the resin composition, and FIG. 2 is a graph illustrating the relationship between gas permeability and flexibility. In the figure, ◯ indicates an example in which a crosslinking agent is used, and... indicates an example in which a crosslinking agent is not used.

Claims (1)

[Claims] 1. A, 45 to 80% by weight of polyamide resin, B, 20 to 5% of elastomer having an anionic polar group.
5% by weight as a main component, C, a predetermined amount of fatty acid as a crosslinking aid, D, a predetermined amount of a crosslinking agent, and is obtained by causing a crosslinking reaction. 2. The thermoplastic resin composition according to claim 1, wherein a metal oxide is used as the crosslinking agent. 3. The thermoplastic resin composition according to claim 1, wherein an amine is used as the crosslinking agent.