JPH0252941B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a new and useful rubber-modified styrenic resin composition, and more particularly, to a rubber-modified styrenic resin composition containing a specific organopolysiloxane and a comb copolymer. Become. Including various light electrical equipment housings, rotating bodies, keyboards,
The present invention relates to an impact-resistant rubber-modified styrenic resin composition with excellent surface smoothness and sliding wear properties (flour resistance), which is used to obtain molded products such as gears or bearings. [Prior Art] Styrenic polymers are one of the thermoplastic resins that have a wide range of uses, but the biggest drawback of the styrenic polymer resins is that they have poor impact resistance. Therefore, in order to eliminate or improve these drawbacks, attempts have been made to polymerize styrenic monomers in the presence of rubbery polymers, and by doing this, styrenic resins with high impact strength can be produced. It has been known for a long time that this type of rubber-modified styrenic resin can be obtained, and due to its high impact strength, it has been widely used for daily necessities, toys, food containers, housings for various light electrical appliances, and lactic acid beverage containers. It has reached the point where By the way, in recent years, technological innovation in the field of light electrical equipment or electronics has been remarkable, and in order to make audio-related equipment and office automation-related equipment lighter or more compact, as well as to reduce costs, various types of rotating bodies and keyboards are being introduced. There is a growing trend towards the use of plastics in gears, bearings, etc. In this field, molded products are required to have various properties such as excellent surface smoothness, impact resistance, and abrasion resistance, and for this reason engineering plastics such as polyacetal are currently used. Therefore, as demand expands in these fields, it is strongly desired to further reduce costs in the future. On the other hand, techniques for obtaining impact-resistant resin compositions with excellent surface smoothness and abrasion resistance by incorporating organopolysiloxane into rubber-modified styrenic resins are already known.
By using a rubbery polymer with a specific microstructure and adjusting the average particle size to fall within a specific range, and by incorporating organopolysiloxane, the surface smoothness and abrasion resistance are further improved. We have already filed an application (Japanese Patent Application No. 72884/1984). [Problems to be Solved by the Invention] However, the resin obtained by the method described in Japanese Patent Application No. 59-72884 has poor wear resistance when used for a certain specific purpose. Furthermore, it is still not satisfactory in terms of durability, and therefore improvements are strongly desired. In other words, when used in structural parts that continuously come into contact with metal or various plastics, such as VTR cassette reels, personal computers, push phones, and various key tops, the wear resistance gradually deteriorates as reciprocating or rotating motion continues for a long period of time. This reduces the effectiveness of the adhesive and causes a phenomenon in which the scraped resin forms powder on the contact surface (“powdering”), which can cause serious problems with the VTR image and the sliding properties of the key top. We often experience that this can cause serious problems in the performance of the equipment itself. [Means for Solving the Problem] Therefore, in view of the existence of various drawbacks in the prior art as described above, the inventors of the present invention conducted intensive studies to eliminate such drawbacks and to meet the demands of the industry, and as a result, the present inventors developed a rubber By incorporating a specific organopolysiloxane and a comb copolymer into a rubber-modified styrenic polymer resin obtained by graft polymerizing a styrenic monomer in the presence of a solid polymer, the aforementioned resin can be produced. We have completed the present invention by discovering that a rubber-modified styrenic resin composition can be obtained in which dusting phenomenon is suppressed and sliding wear characteristics are dramatically improved. That is, the present invention includes (a)97~ as essential components.
A rubber-modified styrenic resin obtained by polymerizing a mixture of 85% by weight of styrene monomer and 3 to 15% by weight of a rubbery polymer, and (b) a viscosity of 100 to 30,000 centistokes at 25°C. The general formula becomes [However, R in the formula is a monovalent organic group selected from the group consisting of an alkyl group, a haloalkyl group, an aryl group, a haloaryl group, and an aralkyl group,
R′ and R″ represent a phenyl group or a C ₁ to C ₆ alkyl group, which may be the same or different, and m is the number of polysiloxane units that this organopolysiloxane should maintain in a liquid state at room temperature. ] Organopolysiloxane represented by (c) The main chain part is composed of a polymer of styrene monomer and the side chain part is composed of a polymer of acrylate monomer. comb-shaped copolymer and rubber-modified styrenic resin.
Organopolysiloxane (b) is contained in a proportion of 0.25 to 1.25 parts by weight as silicon content, and comb copolymer (c) is contained in a proportion of 0.3 to 5 parts by weight based on 100 parts by weight of (a). The object of the present invention is to provide an impact-resistant rubber-modified styrenic resin composition which has particularly excellent surface smoothness and sliding abrasion properties. Here, styrene is suitable as the above-mentioned styrene monomer, but there are other α-
Typical examples include nuclear alkylated styrenes such as methylstyrene or p-methylstyrene; nuclear halogenated styrenes such as 2,4,6-tribromostyrene or 2,4,6-trichlorostyrene, or various mixtures thereof. Can be mentioned. These styrenic monomers, such as acrylic acid or methacrylic acid or their alkyl esters, acrylonitrile or methacrylonitrile, may be used in an amount of about 30% by weight, preferably up to 10% by weight. There is no problem in using some monomers and copolymerizable monomers together. Next, the rubbery polymers mentioned above include butadiene polymers (polybutadiene), copolymers with various vinyl monomers (styrene, acrylonitrile, etc.) copolymerizable with butadiene, and ethylene-propylene-diene. Typical examples include block copolymers of butadiene and various aromatic vinyl compounds, and polymers of acrylic esters. The usage ratio of the styrene monomer and the rubbery polymer is 85 to 97% by weight, preferably 88 to 97% by weight, based on the total amount of these two raw material components.
~95% by weight of styrenic monomer, on the other hand 15~3%
It is suitable that the rubbery polymer accounts for 12 to 5% by weight, preferably 12 to 5% by weight. If the amount of rubbery polymer used is less than 3% by weight, the impact resistance and abrasion resistance will be significantly reduced, and if it exceeds 15% by weight, the abrasion resistance will be reduced. Not only that, but the rigidity of the rubber-modified styrenic resin obtained is also significantly impaired, so neither is preferable. On the other hand, the above-mentioned organopolysiloxane (b) is represented by the general formula [] as shown above, among which representative ones include polymethylphenylsiloxane, polydimethylsiloxane, and polychloropropylmethylsiloxane. , various copolymers such as polytrichloromethylsiloxane or methylphenyldimethylsiloxane, which may be used alone or in combination of two or more. The kinematic viscosity of the organopolysiloxane (b) at 25° C. is suitably in the range of 100 to 30,000 centistokes, preferably 300 to 20,000 centistokes. If this viscosity is less than 100 centistokes, the desired effect of the present invention cannot be achieved, and conversely, if it exceeds 30,000 centistokes, it will not be possible to achieve the desired effect of the present invention. Both are undesirable because it becomes extremely difficult to achieve uniform dispersion, and furthermore, it impairs workability on site. The amount of organopolysiloxane (b) used is as follows:
The silicon content is suitably used in a ratio of 0.25 to 1.25 parts by weight, preferably 0.4 to 1.0 parts by weight, based on 100 parts by weight. If the amount added is less than 0.25 parts by weight,
No substantial addition effect can be expected; on the other hand, 1.25
If the amount exceeds 1 part by weight, the whitening of the molded product of the resulting resin composition will become significant, impairing the appearance, and will cause major problems when trying to obtain colored molded products. Both are unfavorable. The above-mentioned comb copolymer (c) means that the main chain portion is composed of a polymer of styrene monomers as mentioned above, while the side chain portion is composed of methyl acrylate, ethyl acrylate, n-butyl acrylate, etc. Acrylate or acrylic acid ester (acrylate monomer) such as 2-ethylhexyl acrylate
The comb copolymer (c) is used in an amount of 0.3 to 5 parts by weight per 100 parts by weight of the rubber-modified styrene resin (a). A suitable ratio is 0.5 to 3 parts by weight, preferably 0.5 to 3 parts by weight. If the amount added is less than 0.3 parts by weight,
The sliding wear properties (flour resistance), which is one of the objectives of the present invention, may not be sufficient, and conversely, if the amount exceeds 5 parts by weight, the heat resistance will decrease, and the use of the composition of the present invention Both are undesirable because they cannot be used for any purpose. The resin composition of the present invention comprises the rubber-modified styrenic resin (a) listed above, the organopolysiloxane
(b) and a comb-shaped copolymer (c) as essential components, the rubber-modified styrenic resin (a) containing organopolysiloxane (b),
Furthermore, regarding the mechanism of improvement in sliding wear characteristics by including the comb copolymer (c),
Although it is not certain at present, we can speculate as follows. Organopolysiloxane originally has poor solubility (compatibility) with both the rubbery polymer phase and the polystyrene phase, so it bleeds onto the surface of the molded product and imparts lubricity to the organopolysiloxane. will be done. However, metal and the rubber-modified styrene resin
At the sliding part where (a) came into contact, the organopolysiloxane is gradually peeled off from the resin surface and the resin (a)
It is thought that the effectiveness of the organopolysiloxane is lost because the organopolysiloxane migrates to the outside together with the wear particles. Even if the amount of organopolysiloxane (b) added is increased as one of the solutions, the occurrence of dusting cannot be suppressed to a great extent, and the mechanical strength of the rubber-modified styrenic resin (a) is unnecessarily reduced. Just let it happen. By the way, the coexistence of the comb copolymer (c) in these systems suppresses the peeling of the organopolysiloxane (b) from the resin (a), so that the sliding wear characteristics in question are maintained. It will probably become. In obtaining the resin composition of the present invention, first, the method for preparing the rubber-modified styrenic resin (a) is as follows:
Conventional methods such as continuous bulk polymerization or bulk-suspension two-stage polymerization can be applied as they are. Next, the method of adding the organopolysiloxane (b) is not particularly limited, and it may be added in any step of the polymerization step or extrusion step in preparing the rubber-modified styrenic resin. In the process of preparing rubber-modified styrenic resin (a), it is added during the so-called phase transition phenomenon in which the rubbery polymer transitions from the continuous phase to the dispersed phase as the polymerization reaction progresses. This is a particularly desirable method for developing wear resistance. Furthermore, the method of incorporating the comb-shaped copolymer (c) described above into the rubber-modified styrenic resin (a) is not particularly limited, but preferably, the styrenic monomer is added in the presence of a rubbery polymer. When graft copolymerizing, there is a method of adding an acrylate macromonomer at the same time to form and contain the comb-shaped copolymer (c), or from an acrylate macromonomer and a styrene monomer. There is a method in which the comb copolymer (c) is obtained in advance by a known synthesis method and the comb copolymer is incorporated into the resin (a), and any method may be used. As in the case of addition of organopolysiloxane (b), the polymer (c) may be added during either the polymerization process or the extrusion process, and preferably during the phase transition phenomenon. It is appropriate that the The rubber-modified styrene resin composition obtained in this way has extremely excellent surface smoothness and sliding abrasion properties (flour resistance), so its range of application is wide, including cassette tapes and cassette reels for VTRs. , under guides for VTRs, keyboards or keytops for personal computers, rotating stands for personal computer displays, rails for building materials, gears for toys, etc. [Example] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In the following, all parts and percentages are based on weight unless otherwise specified. Further, various physical property tests on the resin composition were conducted in the following manner. (1) Melt flow rate: Based on JIS K-7210. (2) Izod impact value: Based on JIS K-7110. (3) Vikatsu softening point: Based on JIS K-7206. (4) Abrasion resistance (common materials): Abrasion tests were conducted on the common materials using a Taber abrasion tester at a load of 1 kg and a rotational speed of 15,000 mm/min for 60 minutes. It is expressed in amount (mm ³ ). (5) Sliding wear characteristics (a) Wear resistance due to rotation The test piece was placed and fixed on a rotating table, and a stainless steel plate was attached on top of it so that the load was 200 g.
The rotary table was rotated at 750 rpm for 2 hours, and the dusting condition was expressed as the wear rate (%) of the pivot portion. (b) Abrasion resistance by shaking method A test piece was fixed in a shaker, a stainless steel weight was placed so that the load was 200 g, and reciprocating motion was performed at 15 rpm for 2 hours. is expressed in terms of wear amount (mm ³ ). (6) Wear coefficient: Test specimens placed on a sliding surface using a ``Tensilon'' tensile tester at a crosshead speed of 800 mm/
It was measured by pulling it horizontally under the condition that the load was 400 g. Example 1 "BR-02K" [polybutadiene manufactured by Nippon Gosei Rubber Co., Ltd.] 4.2 kg styrene 60 kg tert-dodecyl mercaptan 48 g were charged into a polymerization tank with an internal volume of 120 mm and equipped with a stirrer, and the mixture was heated to 65°C with stirring. The mixture was warmed to a homogeneous solution over 6 hours. Next, the temperature was raised to 110°C and a polymerization reaction was carried out for 7 hours to obtain a prepolymer. After that, 0.75 parts of "SH-200 oil" (polydimethylsiloxane manufactured by Toray Silicone Co., Ltd.; 10,000 centistoxane) was added as a silicon content to 100 parts of this prepolymer, and then "macromonomer
Add 2 parts of a comb-shaped copolymer synthesized from MM-5(H) (acrylic macromonomer manufactured by Toagosei Kagaku Kogyo Co., Ltd.) and a styrene monomer and mix uniformly. The mixture thus obtained was then added to a polymerization tank with an internal volume of 200 and equipped with a stirrer and dispersed in the form of particles into an aqueous phase of the following composition prepared in advance. Water 100 parts Polyvinyl alcohol 0.2 parts Tertiary calcium phosphate 3 parts 2-ethylhexyl sulfate 0.02 parts To this suspension and dispersion were further added 0.1 part of tert-butyl peroxybenzoate and 0.1 part of di-tert-butyl peroxide. for 3 hours at 115°C.
Then, a polymerization reaction was carried out at 130°C for 3 hours. The thus obtained suspended particles of the resin composition of the present invention were washed with water, dried, and then pelletized using an extruder. Next, test pieces are prepared by applying the pellets to an injection molding machine, and the wear resistance (component wear amount), sliding wear characteristics (powdering resistance), friction coefficient, Izod impact value, and Vikat softening point are evaluated. At the same time, the melt flow rate of the pellets was also measured and is summarized in Table 1. The above comb-shaped copolymer was prepared by charging 25 parts of "macromonomer MM-5 (H)", 25 parts of styrene, 50 parts of toluene, and 1.0 part of azobiscyclohexane carbonitrile into a reaction tank, and heating it for 90 minutes under a nitrogen gas atmosphere. After reacting at °C for 5 hours, the resulting reaction solution was
Pour into 10 times the volume of methanol to precipitate, and heat at 80°C.
A styrene-butyl acrylate comb copolymer (number average molecular weight 13,000, weight average molecular weight 71,000 by GPC) obtained by drying under reduced pressure was used. Comparative Example 1 A control resin composition was obtained in the same manner as in Example 1, except that no comb copolymer was used, and then the physical properties were evaluated. The results are summarized in Table 1. Examples 2 to 4 and Comparative Examples 2 and 3 Comb copolymer (c) In Examples 3 and 4, the amounts of organopolysiloxane (b) and comb copolymer (c) were changed, respectively.
In the case of Comparative Example 3, a resin composition was obtained in the same manner as in Example 1, except that the amount of organopolysiloxane (b) used was changed, and then the physical properties were evaluated. I did this. The results are summarized in the same table. Example 5 A rubber-modified styrenic resin was obtained in the same manner as in Example 1, except that the addition of "SH-200 oil" and the comb copolymer was omitted. 100 parts of this rubber-modified styrenic resin, "SH-200
2.0 parts of "Oil" (0.75 parts as silicon content) and 2.0 parts of the same comb copolymer as in Example 1 were melt-kneaded in a twin-screw extruder to form pellets, and the physical properties were evaluated in the same manner as in Part 1. . The results are summarized in Table 1. Example 6 Example 3 except that the addition of the comb copolymer was omitted.
A rubber-modified styrenic resin composition containing "SH-200 oil" was obtained in the same manner as above. 102.6 parts of this rubber-modified styrene resin composition (silicon content: 1.0 parts) and 3.0 parts of the same comb copolymer as in Example 1 were melt-kneaded in a twin-screw extruder,
It was made into pellets, and the physical properties were evaluated in the same manner as in Example 1. The results are summarized in Table 1. Comparative Examples 4 and 5 In the case of Comparative Example 4, general-purpose commercially available heat-resistant HIPS,
In the case of Comparative Example 5, the physical properties were evaluated in the same manner as in Example 1, except that a commercially available ABG for VTR reels was used. The results are summarized in Table 1.

〔Effect of the invention〕

As is clear from the results shown in Table 1,
The resin composition of the present invention has excellent surface smoothness and sliding wear properties. Moreover, it has excellent impact resistance.

Claims (1)

[Claims] 1. 100% of rubber-modified styrenic resin (a) obtained by polymerizing a mixture of 3-15% by weight of a rubbery polymer dissolved in 97-85% by weight of a styrenic monomer.
A general formula with a viscosity of 100 to 30,000 centistokes at 25°C based on parts by weight. [However, R in the formula is a monovalent organic group selected from the group consisting of an alkyl group, a haloalkyl group, an aryl group, a haloaryl group, and an aralkyl group,
R′ and R″ represent a phenyl group or a C ₁ to C ₆ alkyl group, which may be the same or different, and m is the number of polysiloxane units that this organopolysiloxane should maintain in a liquid state at room temperature. ] Organopolysiloxane (b) represented by 0.25 to 1.25 parts by weight as silicon content, and the main chain portion is composed of a polymer of styrene monomer,
A comb-shaped copolymer (c) containing 0.3 to 5 parts by weight of a comb-shaped copolymer (c) whose side chain portion is composed of an acrylate monomer, has excellent surface smoothness and sliding wear resistance. Impact rubber-modified styrenic resin composition.