JP3086389B2 - Expandable particles comprising acrylonitrile / styrene copolymer and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to acrylonitrile
The present invention relates to expandable resin particles made of a styrene copolymer, and to a method for producing such expandable resin particles.

[0002]

2. Description of the Related Art An acrylonitrile-styrene copolymer (hereinafter, referred to as an AS resin) is an improved polystyrene (hereinafter, referred to as a PS resin).
It is said. The reason is that AS resin is better than PS resin,
This is because various physical properties such as heat resistance, oil resistance, chemical resistance, weather resistance, and mechanical strength are excellent.

[0003] The fact that AS resin has better heat resistance than PS resin means that it is difficult to heat and process AS resin, and that it has excellent oil resistance and chemical resistance. This means that AS resins are less likely to absorb aliphatic hydrocarbons such as blowing agents and halogenated aliphatic hydrocarbons. Therefore, it is more difficult to impregnate the AS resin with a foaming agent to form foamable particles than the PS resin. In addition, even if it is made into expandable particles, it is difficult to expand the particles. So, although some attempts have been made to make AS resin into expandable particles,
It has advantages and disadvantages and has not yet been used.

For example, Japanese Patent Application Laid-Open No. 1-272642 discloses that AS resin particles containing 15 to 35% by weight of acrylonitrile and styrene as the remainder are added with cyclopentane, trichloromonofluoromethane or trichlorotrifluoroethane as a blowing agent at high temperature and high pressure. It has been proposed to include as below foamed particles made of AS resin. However, among these blowing agents, trichloromonofluoromethane and trichlorotrifluoroethane, when released into the atmosphere, destroy the ozone layer surrounding the earth and are therefore used because they deteriorate the global environment. Regulated.
The remaining cyclopentane does not cause a problem of deteriorating the global environment, but has a poor foaming ability and cannot firmly fuse the pre-expanded particles, and thus does not give a high-quality foam molded article. This proposal has drawbacks in this respect.

[0005] JP-A-6-73225 discloses a foaming agent in which the above-mentioned disadvantages are improved. The publication uses an AS resin in which acrylonitrile is copolymerized at a ratio of 15 to 35% by weight and styrene is a copolymer at a ratio of 65 to 85% by weight, as in the case of the above-mentioned AS resin.
It has been proposed to use a mixture of up to 95% by weight and 40 to 5% by weight of butane, and to incorporate the mixture into the above resin to form expandable particles made of AS resin. According to this proposal,
Indeed, expandable particles having high expandability can be obtained. However, this proposal has the disadvantage that it is still difficult to include a blowing agent.

The drawback that a foaming agent is hardly contained is not limited to JP-A-6-73225. JP 1
The method of -272642 has the same disadvantage. Both publications heat the AS resin particles to a high temperature for a long time in an attempt to include a foaming agent in the evidence. That is, in the examples of both publications, the AS resin particles are suspended in an aqueous medium, and the suspension is heated at 130 ° C. for 10 hours to contain the foaming agent. In order to impregnate the foaming agent at such a high temperature, the resin particles adhere to each other in the impregnation process to form an agglomerate, which impedes the impregnation of the foaming agent.

In order to prevent this, in the above two publications,
An anticoagulant such as magnesium oxide is to be added. Therefore, an extra operation is required again. That is, since the agglomeration inhibitor adheres to the surface of the resin particles, it must be removed by washing, and since the adhesion is strong, complicated work is required. Therefore,
Without such a complicated operation, it was necessary to incorporate a foaming agent into the AS resin by a simpler method.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to facilitate the impregnation of an AS resin with a foaming agent under the above-described circumstances.

[0009]

Means for Solving the Problems In order to solve the above problems, the present inventor studied a method of impregnating an AS resin with a foaming agent. At the same time, a foaming agent that can be easily impregnated into the AS resin was searched. As a result, they have found that a fluorinated hydrocarbon represented by the structural formula of CF ₃ —CHF—CHF ₂ has a large affinity for an AS resin and can be impregnated particularly easily. As a result of further study with this motivation, they have found that a compound represented by the molecular formula C ₃ F ₆ H ₂ can be easily impregnated into an AS resin. The present invention has been completed based on such knowledge.

[0010] In one aspect, the present invention provides expandable particles made of an AS resin. The expandable particles are
Acrylonitrile (hereinafter referred to as AN) is 15 ~
50% by weight of styrene (hereinafter referred to as ST)
AS resin 100 copolymerized at a ratio of 0 to 85% by weight
In parts by weight, characterized in that the moistened 1-20 parts by weight of fluorinated hydrocarbons represented by the molecular formula C ₃ F ₆ H _2.

Another object of the present invention is to provide a method for producing expandable particles comprising an AS resin. The production method is such that AN is 15 to 50% by weight and ST is 50 to 8%.
The AS resin particles copolymerized at a ratio of 5% by weight are dispersed in an aqueous medium, and this is placed in a closed container, and a fluorocarbon represented by the molecular formula C ₃ F ₆ H ₂ is introduced into the container. Then, the aqueous medium is stirred and the fluorohydrocarbon is injected into the AS resin at a temperature of 50 to 80 ° C.

The most important feature of the present invention is that the AS resin is impregnated with a fluorocarbon represented by the molecular formula C ₃ F ₆ H ₂ as a foaming agent. Among them, the AS resin is a copolymer of AN and ST. This resin is rich in ST, with ST occupying 50-85% by weight and AS occupying 50-15% by weight in the AS resin. A
The reason why the S resin is limited to the one having such a monomer ratio is that when the content of AN is 15% by weight or less, the characteristics of the AS resin due to the addition of AN are difficult to appear, and conversely, when the content of AN is 5% by weight.
Those with 0% by weight or more are not only difficult to manufacture,
This is because it is difficult to foam. Here, ST is not limited to styrene, and may be a styrene derivative such as α-methylstyrene, chlorostyrene, divinylbenzene, or the like.

The above-mentioned AS resin is used as particles. The size of the particles is preferably about 0.5 to 5 mm. Such particles can be easily produced by putting the AS resin into an extruder, extruding it into a string, and cutting the extruded material.

The molecular formula C ₃ F ₆ H used as a blowing agent
_More specifically, the fluorinated hydrocarbon represented by ₂ contains the following three isomers. CF ₃ —CHF—CHF ₂ [Formula 1] CF ₃ —CH ₂ —CF ₃ [Formula 2] CF ₃ —CF ₂ —CH ₂ F [Formula 3] These may be used alone or as a mixture. it can.

The fluorinated hydrocarbon represented by the formula (1) has a boiling point of about 6.5 ° C., and its solubility parameter (hereinafter referred to as SP value) is calculated by the Fedors method. 0.9 (cal / cm ³ ) ^1/2 (hereinafter, this unit is represented by D). The SP value of the fluorinated hydrocarbon represented by Formula 2 is 10.4 D, and the SP value of the fluorinated hydrocarbon represented by Formula 3 is 9.9 D.

The present inventor has proposed that various fluorocarbons be converted to AS
Results impregnated in resin, having a molecular formula C ₃ F ₆ H ₂ exhibits a greater affinity to the AS resin, too great affinity to the other fluorinated hydrocarbons such as CH ₂ FC F _3, etc. in the AS resin Is not shown. Therefore, in the present invention, among the fluorinated hydrocarbons, those having an SP value in the range of 9.0 to 11.0 are selected and used. Incidentally SP value of _CH 2 FCF ₃ is 8.7.

The fluorinated hydrocarbon represented by the molecular formula C ₃ F ₆ H ₂ has a property that it is very easy to penetrate into the AS resin.
That is, a PS resin containing no AN at all is only 0.5% by weight when immersed in a fluorohydrocarbon represented by the formula 1 at 50 ° C. for 5 hours. It is only about 1.7% by weight. Accordingly, the obtained particles do not foam even when heated. However,
The fluorinated hydrocarbon already contained 8.6% by weight of AS resin containing 15% by weight of AN resin when immersed at 50 ° C. for 5 hours, and 17% when immersed at 80 ° C. for 5 hours. .2% by weight. The particles thus obtained foam when heated, and a foamed molded article can be further formed from the expanded particles.

The fluorinated hydrocarbon represented by the formula 1 is represented by A
AS resin having different N content is placed at 50 ° C. or 80 ° C.
For 5 hours, the amount impregnated in the AS resin becomes AN
It shows a peculiar change with the content. In other words, the higher the impregnation temperature is, the more the impregnation amount of 80 ° C. is obviously higher than that of 50 ° C., but the AN content in the AS resin changes from 15% by weight to 50% by weight. In the meantime, initially the amount contained in the AS resin increases as the AN content increases, but the impregnation amount reaches a maximum value when the AN content is 30 to 40% by weight, and thereafter the AN content increases. The amount of impregnation also tends to decrease. However, the impregnated resin still shows a high impregnation amount of at least 9% by weight or more, so that the impregnated resin has sufficient foaming ability. If this relationship is tabulated,
Table 1 shows the results.

[0019]

[Table 1]

The fluorocarbon represented by the molecular formula C ₃ F ₆ H ₂ has such a property that it is very easy to be contained in the AS resin as compared with other fluorocarbons. As an example, an AS resin having an AN content of 24% by weight is immersed in a fluorinated hydrocarbon (a) represented by the formula 1 and a fluorinated hydrocarbon (b) represented by the structural formula CFH ₂ -CF _3. When the impregnation amounts of these fluorinated hydrocarbons are compared, the former is much higher than the latter.

More specifically, A having an AN content of 24% by weight
Using S resin, the impregnation temperature is 50, 80, 100, 1
20 ° C and the impregnation times were 5, 10, 24, 4
When the time was changed to 8 hours, the amount (impregnation amount) at which the above-mentioned fluorinated hydrocarbon (a) and the fluorinated hydrocarbon (b) were contained in the AS resin was shown in the table. Table 2 shows the results. Further, when the AS resin having an AN content of 45% by weight was brought into contact in the same manner as above, the impregnation amounts of the above-mentioned fluorinated hydrocarbons (a) and (b) are shown in the table. When,
Table 3 shows the results. This makes it clear that fluorinated hydrocarbons (a) are much easier to impregnate than other fluorinated hydrocarbons.

[0022]

[Table 2]

[0023]

[Table 3]

In addition, the fluorocarbon (a) used in the present invention contains about 10% by weight of a foaming agent at an impregnation temperature of 50 to 80 ° C. and an impregnation time of 5 hours, and is sufficiently foamed. It is intended to be used as a practical particle. Increasing the temperature further or impregnating for a longer time does not increase the impregnation much. Therefore, foamable particles suitable for practical use can be obtained by an impregnation operation at a temperature of about 50 to 80 ° C. for about 5 hours.

On the other hand, in the case of fluorinated hydrocarbon (b), even if impregnated at 50 ° C. for 48 hours, foamable particles suitable for practical use can be obtained at an impregnation amount of about 3% by weight or less. Absent. In this case, even if the impregnation time is extended from 10 hours to 48 hours, the impregnation amount does not greatly increase. Increasing the impregnation temperature from 80 ° C. to 100 ° C. increases the impregnation amount, but increasing the impregnation temperature from 100 ° C. to 120 ° C. rather decreases the impregnation amount. Therefore, the impregnation temperature can be increased to around 100 ° C. to increase the impregnation amount, but the impregnation amount is still small, and the obtained expandable particles do not have sufficient foaming ability. Therefore, from this comparison, C ₃ F ₆ H
It turns out that ₂ is an excellent foaming agent for AS resin.

[0026]

As described above, since C ₃ F ₆ H ₂ has a large amount of impregnation with the AS resin, it has a special affinity for the AS resin, and therefore remains in the expandable particles. The performance is large, and the obtained expandable particles have a sufficient storage period and are suitable for practical use. Further, the obtained expandable particles are stored in a cool box for several days, and then heated to a temperature higher than the softening point of the AS resin by contacting steam with the stored expandable particles to largely expand into pre-expanded particles. After aging for several hours, the pre-expanded particles are placed in a mold for foam molding and heated by passing steam to form a foam molded article. This foamed molded product has 50 parts depending on the content of the foaming agent.
It can be swelled up to about twice. In this way, an AS resin foam with good fusion of the particles and good appearance can be obtained. And since the obtained foam is made of AS resin, heat resistance, oil resistance, chemical resistance,
It has excellent weather resistance and mechanical strength. The expandable particles according to the present invention provide a great advantage in such a point.

Further, the method for producing expandable particles according to the present invention is advantageous in that expandable particles giving the above-mentioned benefits can be easily produced.

Hereinafter, the present invention will be described more specifically with reference to examples.

[0029]

Example 1 300 liters of water in a 5 liter autoclave
0 g, 1000 g of AS resin (manufactured by Asahi Kasei Corporation, Stylac AS # 76 7 ) having an AN content of 24% by weight,
The resin was dispersed in water with stirring. At this time, the coagulation inhibitor that has been used so far was not added. While stirring, 350 g of a fluorinated hydrocarbon represented by Formula 1 was injected as a foaming agent, and the temperature was raised to 50 ° C. At this time, the internal pressure of the autoclave was 5.2 kg / cm ² (G).

After impregnation at 50 ° C. for 5 hours, the mixture was cooled to 15 ° C., and the AS resin containing a foaming agent was taken out. AS
The resin was good without any agglomeration. The resulting AS resin contained 10.2% by weight of a blowing agent.

After leaving the AS resin in a refrigerator kept at 10 ° C. for 3 days, 30 times pre-expanded particles were obtained by steam. After leaving the pre-expanded particles at room temperature for 24 hours, the pre-expanded particles are placed in a molding die, and 0.5 kg / c
m ² (G) water vapor was introduced for secondary foaming to obtain a foam molded article. The obtained foamed molded article had good appearance in which the foamed particles were fused well to each other. This foam molded article was superior to conventional PS foam molded articles in heat resistance, mechanical strength, and the like.

[0032]

Example 2 Same impregnation temperature of 80 ° C. as in Example 1.
The procedure was performed in the same manner as in Example 1 except that In the autoclave, good expandable particles were obtained without adhesion of the AS resin. The resulting expandable particles contained 19.4% by weight of a blowing agent.

When the foamable particles were subjected to foam molding in the same manner as in Example 1, a good foam molded article foamed about 100 times was obtained.

[0034]

Example 3 In Example 1, an AS resin having an AN content of 45% by weight was used, and the impregnation temperature was 80 ° C.
The procedure was performed exactly as in Example 1 except that The resulting expandable particles contained 18.8% by weight of a blowing agent.

The expandable particles were expanded in the same manner as in Example 1 to obtain a foamed molded product. The foamed product was foamed about 60 times to obtain a good foamed molded product.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-272642 (JP, A) JP-A-61-40335 (JP, A) JP-A-7-292148 (JP, A) JP-A-6-292148 73225 (JP, A) JP-A-8-59877 (JP, A) JP-A-61-16935 (JP, A) JP-A-62-268749 (JP, A) JP-A-63-268750 (JP, A) JP-A-57-185328 (JP, A) JP-A-6-32933 (JP, A) JP-B-47-4155 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 9/00-9/42

Claims (2)

(57) [Claims] (1) acrylonitrile is 15 to 50% by weight,
Styrene is the copolymerized acrylonitrile-styrene copolymer 100 parts by weight and a proportion of 50 to 85% by weight, moistened to 20 parts by weight of fluorinated hydrocarbons represented by the molecular formula C ₃ F ₆ H ₂ Foamable particles comprising an acrylonitrile / styrene copolymer. 2. An acrylonitrile comprising 15 to 50% by weight,
Acrylonitrile / styrene copolymer particles, in which styrene is copolymerized at a ratio of 50 to 85% by weight, are dispersed in an aqueous medium, and this is placed in a closed container, and the molecular formula C is introduced into the container.
Acrylonitrile / hydrocarbon represented by ₃ F ₆ H ₂ is introduced, and the fluorinated hydrocarbon is injected into the copolymer at a temperature of 50 to 80 ° C. by stirring the aqueous medium. A method for producing expandable particles comprising a styrene copolymer.