JPS6121971B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has significantly better impact resistance than conventional styrene-based resins, and has an excellent appearance.
The present invention relates to a reinforced styrene resin structure that is easy to manufacture and also has excellent heat resistance. Thermoplastic resin containing polystyrene as a continuous phase and diene rubber as a fractional phase is known as high-impact polystyrene, and is used in a wide range of applications due to its excellent properties such as appearance, processing fluidity, and dimensional accuracy. ing. However, since the heat resistance is insufficient, there has been a desire for a resin that has the characteristics of impact-resistant polystyrene and has improved heat resistance. ABS resin is used for applications where the heat resistance of high-impact polystyrene is insufficient until now.
In particular, heat-resistant ABS resin is often used.
However, although heat resistance has been improved with heat-resistant ABS resin, processing fluidity has significantly decreased.
In order to mold thin-walled products or products with complicated shapes, high temperatures are required, which poses problems such as molding problems due to gas generation. On the other hand, in order to improve the heat resistance of high-impact polystyrene, a copolymer consisting of α-methylstyrene is blended with conventional high-impact polystyrene, as described in JP-A-57-31946. Methods are known. Such a modification method provides the same structure as high-impact polystyrene and higher heat resistance, but the impact resistance strength is not necessarily sufficient and its applications are limited. In view of the above, the present inventors have conducted intensive research to further improve the impact resistance of these resins with improved heat resistance. When a block copolymer is made to coexist, this copolymer connects several diene-based graft rubber particles, takes in the particles and a portion of the matrix resin, and forms quite large particles as a whole, which are dispersed in the matrix. As a result, it was found that the impact resistance was significantly improved while maintaining the heat resistance. Furthermore, when a linear styrene-butadiene block copolymer is made to coexist with a styrene resin matrix in which grafted rubber particles with a weight average particle size of 0.05 to 1 micron are dispersed, a plurality of the grafted rubber particles are linked together. It has also been found that the balance between appearance and impact resistance is greatly improved because large particles are formed in which the particles and matrix resin are incorporated. Taking this discovery as an opportunity, the present inventors further extensively studied styrene resins and found that
Compared to any styrene-based resin structure in which only diene-based graft rubber particles are dispersed as small particles, large particles, or a mixture of small and large particles, the small size of diene-based graft rubber is It has been found that a styrenic resin structure containing particles and large particles in which the small particles are wrapped in a linear styrene-butadiene block copolymer has significantly improved impact resistance and appearance. In addition, styrene-butadiene/
It was also found that a resin in which only a block copolymer was dispersed had poor impact resistance and appearance, and that impact resistance was not improved when a non-linear star type styrene-butadiene block copolymer was used. . The present invention has been made based on the above findings. That is, the present invention provides a styrenic resin matrix.
It is composed of 70 to 94% by weight, 5 to 20% by weight of grafted rubber particles with a weight average particle diameter of 0.05 to 1 micron, and 1 to 10% by weight of a linear styrene-butadiene block copolymer. Reinforced by dispersed particles with a weight average particle diameter of 0.1 to 5 microns, characterized by a styrene-butadiene block copolymer forming large particles incorporating a plurality of graft rubber particles and matrix resin. The invention relates to a reinforced styrenic resin structure. It should be noted that the morphology of the large particles, which is the most important part of the present invention, is completely unpredictable from the morphology of the graft rubber particles and the linear styrene-butadiene block copolymer, and shows unique changes. , the expression "styrenic resin structure" was used to distinguish it from a mere styrene resin or a styrene resin composition. The reinforced styrenic resin structure of the present invention has the major features of being excellent in both impact resistance and appearance, and being extremely easy to manufacture. The styrene resin used as the matrix resin in the present invention refers to a thermoplastic resin containing styrene or a styrene derivative as a constituent unit, such as styrene-α-methylstyrene copolymer, styrene-acrylonitrile copolymer (AS
resin), styrene-α-methylstyrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer (MS resin), polyparamethylstyrene, and the like. The above-mentioned styrene-α-methylstyrene-acrylonitrile copolymer is known as a heat-resistant resin, and as a highly preferred form of the styrene-based resin matrix of the present invention, the styrene-based resin matrix is made of styrene 28
~69% by weight, α-methylstyrene 25-45% by weight,
The present invention relates to a reinforced styrenic resin structure with good heat resistance, characterized by comprising 1 to 7% by weight of acrylonitrile. Furthermore, the present invention provides the styrenic resin structure 41
This invention relates to a reinforced styrenic resin structure with good heat resistance, which is made by blending 1 to 99 parts by weight of polystyrene and/or 1 to 59 parts by weight of impact-resistant polystyrene. In the present invention, graft rubber particles are rubber particles obtained by graft polymerizing styrene, α-methylstyrene, acrylonitrile, methyl methacrylate, etc. to polybutadiene rubber containing butadiene as a main component, styrene-butadiene rubber, etc., and the size thereof is It refers to particles with a weight average particle diameter of 0.05 to 1 micron. In the case of particles smaller than 0.05 microns, even if linear styrene-butadiene block copolymer (hereinafter simply referred to as SB block copolymer) is added, the impact resistance of the resin before addition is very low. If it is too low, it has no practical meaning, and if it is larger than 1 micron, the appearance of the resin molded product will be significantly impaired, which is not preferable. A more preferred particle size is 0.1 to 0.5 microns. In the present invention, the particles formed by the SB block copolymer include two or more graft particles.
It has a structure in which less than 100 particles are wrapped around each other, and their size is 0.1 to 5 microns. In the present invention, the SB block copolymer is
General formula (A-B-) _o A (n is 1 to 10) or (A-
B) _n (m is 2 to 5) (where A is a styrene block and B is a butadiene block). A particularly important point in the structure of the present invention is 0.05~
1. Preferably, diene-based graft rubber particles having a particle size of 0.1 to 0.5 microns and an SB block copolymer in a unique particle form coexist,
As a result, a dramatic improvement in impact strength was obtained. As is clear from the electron micrograph in Figure 1 of the attached drawings, the SB block copolymer connects the small particles of graft rubber, incorporates the graft rubber particles and matrix resin, and forms quite large particles, which are then incorporated into the matrix. It was discovered that they form a unique form of dispersion that was previously unknown. Such a unique structure and its effects can of course be considered in cases where the matrix resin is polystyrene, and in other cases as well, but the matrix resin may be the aforementioned styrene, α-methyl, which has high heat resistance but somewhat poor impact resistance. It is particularly effective in improving the impact resistance of heat-resistant resins made of styrene. Furthermore, a secondary effect of the presence of the SB block copolymer is that polystyrene can be easily blended with the heat-resistant resin. Journal of Polymer Science B-3 No. 1007
(1965), when the difference in acrylonitrile content between two types of styrene-acrylonitrile copolymers exceeds 4% by weight, the compatibility decreases; If the acrylonitrile content of the composite is 7% by weight or less, the compatibility with polystyrene will not decrease. Therefore, polystyrene or high-impact polystyrene can be easily blended with the heat-resistant resin. In the reinforced styrene resin structure of the present invention, the content of dispersed graft rubber particles is required to be 5 to 20% by weight based on the matrix resin, and the particle size is 0.05 to 1 micron, preferably 0.1 to 0.5 micron. be. If it is less than 5% by weight, the impact strength of the composition will be low, and if it exceeds 20% by weight, a good appearance will not be obtained. The average particle diameter was determined by taking an electron micrograph using an ultrathin section method and weight-averaging the measured particle diameters. The content of linear styrene-butadiene block copolymer should be between 1 and 10% by weight.
If it is less than 1% by weight, the effect of improving impact resistance will not appear,
If the amount exceeds 10% by weight, a good appearance cannot be obtained. In the reinforced styrenic resin structure of the present invention with good heat resistance, if the α-methylstyrene content in the styrenic resin matrix is less than 25% by weight, sufficient heat resistance cannot be obtained, and if it exceeds 45% by weight, the impact strength is poor. Not only does it decrease, but it also reduces liquidity. If the acrylonitrile content is less than 1% by weight, the thermal stability and impact strength will decrease, and if it exceeds 7% by weight, the processing fluidity will decrease. In addition, by blending the reinforced styrenic resin structure with good heat resistance with polystyrene and/or impact-resistant polystyrene, a reinforced styrenic resin structure with excellent processing flowability without much reduction in heat resistance can be obtained. Obtainable. Blending polystyrene and/or high-impact polystyrene does not substantially change the morphology of large particles in the reinforced styrenic resin structure, so for example, a reinforced styrenic resin structure blended with high-impact polystyrene When observed with an electron microscope, the dispersed particles derived from the reinforced styrene resin structure and the dispersed particles derived from the high-impact polystyrene are extremely uniformly mixed together. If the polystyrene and/or high-impact polystyrene is less than 1 part by weight in the blend, processing fluidity will not be improved;
If it exceeds parts by weight, sufficient heat resistance cannot be obtained. The styrenic resin matrix and grafted rubber particles can be produced by one or a combination of emulsion polymerization, bulk polymerization, and suspension polymerization in the presence of rubber.
Emulsion polymerization is preferred because the weight average particle diameter of the grafted rubber particles is 0.05 to 1 micron. Also, as a method for producing SB block copolymer,
For example, there is a block copolymerization method proposed in Japanese Patent Publication No. 36-19286, in which styrene or butadiene, or a styrene-butadiene mixture is polymerized stepwise in a hydrocarbon solvent using an organolithium compound as an initiator. However, it is not limited to these. Furthermore, polystyrene and/or high-impact polystyrene can be obtained by one or a combination of emulsion polymerization, bulk polymerization, and suspension polymerization. The method for manufacturing the reinforced styrenic resin structure of the present invention includes a method of blending a styrenic resin consisting of a styrenic resin matrix and graft rubber particles with an SB block copolymer, or a method of blending a styrenic resin consisting of a styrenic resin matrix and grafted rubber particles with an SB block copolymer, or a method of blending a styrenic resin comprising a styrenic resin matrix and grafted rubber particles with a SB block copolymer. Examples include a blending method, and any commonly used blending method may be used.
It goes without saying that antioxidants, ultraviolet absorbers, flame retardants, pigments, glass fibers, plasticizers, etc. can be added if necessary at that time, and it can also be made into a solid form using an extruder or the like. As described above, the present invention relates to a reinforced styrenic resin structure made of styrene resin, which has significantly better impact resistance than conventional styrene resins, has an excellent appearance, and is easy to manufacture. Due to its excellent heat resistance, impact strength, processing fluidity, etc., it is expected to be used in a wide range of fields such as automobile parts, industrial parts, and home appliance parts. This will be explained below using examples. Example 1 The inside of a reactor equipped with a stirrer was replaced with nitrogen, and a butadiene copolymer latex (weight average particle size 0.2μ) consisting of 200 parts by weight of ion-exchanged water, 10% by weight of styrene, and 90% by weight of butadiene was prepared. 10 parts by weight in terms of solid content and 2 parts by weight of disproportionated potassium rosinate were added, and the temperature was raised to 80°C. The temperature inside the reactor is 80℃
5% by weight of acrylonitrile, α
- 90 parts by weight of a monomer mixture consisting of 40% by weight of methylstyrene and 55% by weight of styrene and 0.2 parts by weight of tertiary dodecyl mercaptan were added for 5 hours, and in parallel with the monomers, 0.1 parts by weight of potassium persulfate was added to the ions. An aqueous solution consisting of 50 parts by weight of exchanged water was continuously fed to the reactor over a period of 5 hours. Further 80℃ after supply ends
The polymerization reaction was continued for 2 hours to complete the polymerization.
The polymerization rate was determined by measuring the solid content of the polymerized latex and found it to be 98% (based on the monomers supplied). The obtained latex was dropped into a 2% aqueous aluminum sulfate solution and coagulated. Further dehydration,
After drying, add 0.5% by weight of 4,4′-butylidene bis(3-methyl-6-tertiary butylphenol).
was added, and pelletized copolymer (A) was obtained using a vented screw extruder. Copolymers (A) and (A-B) are represented by the general formula ₂ and have a styrene content of 40
After blending styrene-butadiene block copolymer in weight percent in the proportions shown in Table 1 using a vented screw extruder, injection molding was performed to prepare specified test pieces. Table 1 shows the results of measuring physical properties using the prepared test pieces. Note that general high-impact polystyrene is also listed in Table 1 as a comparative example. From the results in Table 1, it can be seen that the reinforced styrenic resin structure according to the present invention has an excellent balance of heat resistance, impact strength, and process fluidity.

[Table] Example 2 Copolymer (A) obtained in Example 1 (A-B)
A styrene-butadiene block copolymer with a styrene content of 40% by weight, represented by the general formula ₂ , (A
-B) ₄
Impact resistance modified with styrene-butadiene block copolymer with a styrene content of 30% by weight and 6% by weight of diene rubber polystyrene, and
Impact-resistant polystyrene modified with 14% by weight of diene rubber was mixed in the proportions shown in Table 2, and a resin pellet was obtained using a vented screw extruder. Next, predetermined test pieces were made from the obtained resin using an injection molding machine, and the physical properties were measured. The results are shown in Table 2. From the results in Table 2, it can be seen that the reinforced styrenic resin structure according to the present invention has an excellent balance of heat resistance, impact strength, and process fluidity.

【table】 [Brief explanation of the drawing]

Figure 1 is an electron micrograph (magnification:
25000). Figure 2 is an electron micrograph showing the internal structure of conventional high-impact polystyrene (magnification
25000).

Claims (1)

[Claims] 1. 70 to 94% by weight of styrenic resin matrix,
It is composed of 5 to 20% by weight of grafted rubber particles with a weight average particle diameter of 0.05 to 1 micron, and 1 to 10% by weight of a linear styrene-butadiene block copolymer. A weight average particle size characterized by the polymer mainly forming large particles incorporating a plurality of graft rubber particles and matrix resin.
Reinforced styrenic resin structure reinforced with dispersed particles of 0.1 to 5 microns. 2 The styrenic resin matrix contains styrene 28
~69% by weight, α-methylstyrene 25-45% by weight,
and 1 to 7% by weight of acrylonitrile, the reinforced styrenic resin structure having good heat resistance according to claim 1. 3 Styrene 28-69% by weight, α-methylstyrene
25-45% by weight, 70-94% by weight of a styrene resin matrix consisting of 1-7% by weight of acrylonitrile, 5-20% by weight of grafted rubber particles with a weight average particle diameter of 0.05-1 micron, and linear styrene.
It is composed of 1 to 10% by weight of butadiene block copolymer, and is a linear styrene-butadiene block copolymer.
Reinforcement reinforced by dispersed particles with a weight average particle size of 0.1 to 5 microns, characterized in that the block copolymer mainly forms large particles in which a plurality of graft rubber particles and matrix resin are incorporated. 41 to 99 parts by weight of styrenic resin structure and 1 to 10 parts of polystyrene and/or impact-resistant polystyrene
59 parts by weight of the graft derived from the reinforced styrenic resin structure in a homogeneous mixture of a polystyrene matrix of polystyrene and/or high-impact polystyrene and a styrenic resin matrix of the reinforced styrenic resin structure. When rubber particles, the dispersed large particles, and impact-resistant polystyrene are blended, the rubber particles derived from impact-resistant polystyrene are further uniformly dispersed, resulting in good heat resistance and process fluidity. Reinforced styrene resin structure.