JP2002275486A - Slidability improving agent and polyolefin resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin composition excellent in sliding properties without damaging merits of a polyolefin and deterioration of molding properties, surface appearance or the like, and provide an improving agent for the same. SOLUTION: This slidability improving agent includes silicone based composite particles obtained by graft polymerizing (B-2) one, two ore more vinyl monomers selected from an aromatic alkenyl compound, an acrylic ester, a methacrylate and a vinyl cyanide compound to (B-1) a silicone rubber including a functional group capable of carrying out a vinyl polymerization. The slidability improving agent is excellent in dispersibility to a polyolefin resin and the polyolefin resin composition compounded with the same manifests improved sliding properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin resin composition having excellent slidability, a method for producing the same, and a modifier therefor.

[0002]

2. Description of the Related Art Polyolefins such as polyethylene and polypropylene are widely used in home electric parts, automobile parts, packaging materials, etc. because of their low cost, light weight, and excellent moldability. However, especially sliding members such as bearings, cams, and gears require high slidability, but ordinary polyolefins do not have sufficient slidability, and wear and the like are likely to occur. Was. Various methods for improving the slidability of a thermoplastic resin containing a polyolefin resin have been studied. For example, there are a method of adding a small amount of lubricating oil such as silicone oil to a thermoplastic resin, a method of adding a layered crystal filler such as molybdenum disulfide and graphite, and a method of adding a small amount of fluororesin.

[0003]

Among these, it is well known that silicone oil is blended with a thermoplastic resin to improve slidability. However, when the blending amount of silicone oil is increased in order to further improve the sliding property,
On the contrary, the extrudability of the extruder deteriorates, and the bleeding to the surface of the molded product becomes excessive and sticky, which may cause the slidability to decrease.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a polyolefin resin composition having excellent slidability without impairing the characteristics of the polyolefin and without deteriorating the moldability and surface appearance. The purpose of the present invention is to provide a product and a modifier therefor.

[0005]

SUMMARY OF THE INVENTION The present invention improves the slidability without bleeding on the surface of a molded product by graft-polymerizing a vinyl monomer easily compatible with a polyolefin resin to a silicone rubber. Things. The slidability modifier of the present invention is a compound selected from aromatic alkenyl compounds, acrylates, methacrylates and vinyl cyanide compounds, based on the vinyl polymerizable functional group-containing silicone rubber (B-1). Alternatively, it contains silicone-based composite particles obtained by graft-polymerizing two or more kinds of vinyl-based monomers (B-2). The polyolefin resin composition of the present invention contains the slidability modifier, and contains 0.1 to 50 parts by mass of the silicone-based composite particles (B) based on 100 parts by mass of the polyolefin resin (A). A resin composition, comprising silicone-based composite particles (B)
Is a silicone rubber having a vinyl polymerizable functional group (B-1)
With one or more vinyl monomers (B) selected from aromatic alkenyl compounds, acrylic esters, methacrylic esters and vinyl cyanide compounds
-2) is obtained by graft polymerization.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin resin composition of the present invention comprises a polyolefin resin as the component (A) and a predetermined amount of silicone composite particles as the component (B) as a slidability modifier. It is. Examples of the polyolefin resin as the component (A) include an α-olefin homopolymer or a copolymer of two or more α-olefins.
As the α-olefin, those having about 2 to 20 carbon atoms are usually used, and specifically, for example, ethylene, propylene, 1-butene, 4-methyl 1-pentene, hexene, 1-octene, 1-decene , 1-dodecene, 1-tetradecene and the like. Specifically, such polyolefins include, for example, low density polyethylene, high density polyethylene, polypropylene, poly 1-butene,
Examples thereof include poly-4-methyl 1-pentene, a random copolymer of ethylene and propylene, and a block copolymer. The α-olefin copolymer may be any of a random copolymer, a block copolymer and a graft copolymer, and may be a mixture of these various polyolefins.

The silicone rubber (B-1) constituting the silicone-based composite particles as the component (B) of the present invention is a polyorganosiloxane characterized by having a vinyl polymerizable functional group. Preferably, it is a polyorganosiloxane having a vinyl polymerizable functional group and further having a crosslinked structure via a siloxane bond. Although the size of the polyorganosiloxane particles is not particularly limited, the weight-average particle size is preferably from 0.02 μm to 0.5 μm, more preferably 0. 0.05 μm to 0.3 μm.
This polyorganosiloxane is a mixture of a diorganosiloxane and a siloxane containing a vinyl polymerizable functional group,
Or, if necessary, a homomixer that atomizes a latex obtained by emulsifying a mixture containing a siloxane-based cross-linking agent with an emulsifier and water with a shearing force by high-speed rotation, a homogenizer that atomizes with a jet force of a high-pressure generator, and the like. After use and micronization, polymerization can be carried out at a high temperature using an acid catalyst, and then the acid can be neutralized with an alkaline substance to produce the compound.

Examples of the diorganosiloxane used in the production of the polyorganosiloxane include a diorganosiloxane cyclic body having three or more membered rings, a linear polysiloxane having a low degree of polymerization, and the like. Siloxane is preferred. Specific examples include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and the like. These may be used alone or as a mixture of two or more.

The siloxane containing a vinyl polymerizable functional group is a siloxane containing a vinyl polymerizable functional group and capable of bonding to a diorganosiloxane via a siloxane bond. Considering the reactivity with the diorganosiloxane, Various alkoxysilane compounds containing a vinyl polymerizable functional group are preferred. Specifically, β-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylethoxydiethylsilane,
methacryloyloxysiloxanes such as γ-methacryloyloxypropyldiethoxymethylsilane and δ-methacryloyloxybutyldiethoxymethylsilane, vinylsiloxanes such as tetramethyltetravinylcyclotetrasiloxane, p-vinylphenyldimethoxymethylsilane, and γ-mercaptopropyldimethoxy Mercaptosiloxanes such as methylsilane and γ-mercaptopropyltrimethoxysilane are exemplified. In addition, these vinyl polymerizable functional group-containing siloxanes can be used alone or as a mixture of two or more. As the siloxane-based crosslinking agent, a trifunctional or tetrafunctional silane-based crosslinking agent such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, or tetrabutoxysilane is used.

The emulsifier used in the production of the polyorganosiloxane according to the present invention is preferably an anionic emulsifier.
An emulsifier selected from sodium polyoxyethylene nonyl phenyl ether sulfate is used. Particularly, sulfonic acid emulsifiers such as sodium alkylbenzene sulfonate and sodium lauryl sulfonate are preferable. These emulsifiers comprise a siloxane mixture 10
It is preferably used in the range of about 0.05 to 5 parts by mass with respect to 0 parts by mass. If the amount of the emulsifier is less than 0.05 part by mass, the dispersion state of the silicone rubber becomes unstable, and it tends to be difficult to maintain the emulsified state with a fine particle diameter.
When the amount of the emulsifier exceeds 5 parts by mass, the coloring of the finally obtained polyolefin resin composition tends to increase due to the residual emulsifier.

The method of mixing a siloxane mixture, an emulsifier, water and / or an acid catalyst includes mixing by high-speed stirring and mixing by a high-pressure emulsifying device such as a homogenizer. A method using a homogenizer is a method of mixing a polyorganosiloxane latex. This is a preferable method because the particle size distribution is reduced. Examples of the acid catalyst used for the polymerization of the organosiloxane include sulfonic acids such as aliphatic sulfonic acids, aliphatic substituted benzenesulfonic acids, and aliphatic substituted naphthalenesulfonic acids, and mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid. These acid catalysts are used alone or in combination of two or more. Among these, aliphatic substituted benzenesulfonic acid is preferred because it is also excellent in stabilizing action of the polyorganosiloxane latex, and n-
Dodecylbenzenesulfonic acid is particularly preferred. Also, n
-When dodecylbenzenesulfonic acid and a mineral acid such as sulfuric acid are used in combination, the coloring of the resin composition caused by the emulsifier component of the polyorganosiloxane latex can be reduced. As a method of adding an acid catalyst used for polymerization, a method of mixing with a siloxane mixture, an emulsifier and water,
There is a method of dropping a latex in which a siloxane mixture is finely divided into a high-temperature aqueous acid solution at a constant rate. The polymerization temperature of the organosiloxane is preferably 50 ° C. or higher, more preferably 80 ° C. or higher. The polymerization time of the organosiloxane is at least 2 hours, more preferably at least 5 hours when the acid catalyst is mixed with the siloxane mixture, emulsifier and water to form fine particles, and more preferably at least 5 hours. In the method of dropping the converted latex, it is preferable to hold the latex for about 1 hour after completion of dropping. Termination of the polymerization can be carried out by cooling the reaction solution and neutralizing the latex with an alkaline substance such as caustic soda, caustic potash, and sodium carbonate.

The silicone composite particles (B) according to the present invention
Is obtained by adding at least one vinyl selected from aromatic alkenyl compounds, methacrylic esters, acrylic esters and vinyl cyanide compounds to the vinyl-polymerizable functional group-containing silicone rubber (B-1) produced by emulsion polymerization as described above. It can be produced by graft polymerization of the system monomer (B-2). Among the vinyl monomer (B-2) units constituting the graft polymerization component, examples of the aromatic alkenyl compound include styrene, α-methylstyrene, and vinyltoluene. Examples of the methacrylate include methyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate and the like. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, and butyl acrylate. Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.

In the graft polymerization, a latex of a vinyl polymerizable functional group-containing silicone rubber (B-1) is added to at least one vinyl monomer selected from an aromatic alkenyl compound, a methacrylate, an acrylate and a vinyl cyanide compound. The polymerization can be carried out in one step or in multiple steps by a radical polymerization technique by adding a monomer. A preferable ratio of the graft polymerization component in the silicone-based composite particles is a vinyl-polymerizable functional group-containing silicone rubber (B-
1) The graft polymerization component (B-
2) It is in the range of 5 to 80% by mass. (However, (B-
1) + (B-2) = 100% by mass) When the use ratio of the graft polymerization component is less than 5% by mass, the obtained silicone-based composite particles have a low compatibility with polyolefin and have a reduced effect on the surface of the molded article. Bleeding may occur. On the other hand, when the content exceeds 80% by mass, the performance of expected performance may be reduced. In addition, various chain transfer agents for adjusting the molecular weight and graft ratio of the graft polymer can be added to the monomers used in the graft polymerization. The silicone-based composite particles which are the component (B) of the present invention are prepared by introducing the graft copolymer latex produced as described above into water in which a coagulant is dissolved,
It can be recovered by solidification. As coagulants, sulfuric acid, hydrochloric acid, inorganic acids such as phosphoric acid and nitric acid,
Metal salts such as calcium chloride, calcium acetate, and aluminum sulfate can be used.

The ratio of the silicone-based composite particles as the component (B) of the present invention to the polyolefin resin (A) is in the range of 0.1 to 50 parts by mass per 100 parts by mass of the polyolefin resin. When the use ratio of the silicone-based composite particles is less than 0.1 part by mass, the expression of expected performance may be reduced, and when it exceeds 50 parts by mass, the original performance of the polyolefin resin may be reduced. Tend to spoil. In the present invention, the silicone-based composite particles (B) are mixed with the polyolefin resin (A) by melt-kneading by a known method such as extrusion kneading or roll kneading. It is also possible to perform multi-stage mixing, for example, by mixing a part of the silicone-based composite particles of the present invention and a polyolefin resin to prepare a master batch, and then adding and mixing the remaining polyolefin resin. The polyolefin resin composition of the present invention can be formed into various molded articles by known thermoforming. Examples of the thermoforming method include injection molding, extrusion molding, calender molding, press molding, transfer molding, hollow molding, flash molding and cast molding, and among them, production by injection molding is preferable.

The silicone composite particles of the present invention have an extremely good dispersibility in a polyolefin resin, and a polyolefin resin composition containing this compound has excellent sliding properties. Further, the means for improving the slidability of a resin by kneading the silicone-based composite particles of the present invention works effectively with a small amount of addition, and thus does not impair the intrinsic physical properties of the resin.

[0016]

EXAMPLES The present invention will be described below with reference to examples. In addition,
In Examples and Comparative Examples, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise specified.
The average particle size of the polymer in the latex is Otsuka Electronics Co., Ltd.
It was determined by a dynamic light scattering method using "DLS-700 model" manufactured by FUJIFILM Corporation.

Various silicone-based composite particles were produced as follows. Example 1 Production of Silicone Composite Particles (C-1) 2 parts of tetraethoxysilane, 0.5 part of γ-methacryloyloxypropyldimethoxymethylsilane and 97.5 parts of octamethylcyclotetrasiloxane were mixed, and a siloxane mixture was obtained. 100 parts were obtained. 100 parts of the above-mentioned mixed siloxane was added to 200 parts of distilled water in which 1 part of sodium dodecylbenzenesulfonate and 1 part of dodecylbenzenesulfonic acid were dissolved, and 10,000 r.
pm, then 30MP with a homogenizer.
The mixture was emulsified and dispersed at the pressure of a to obtain an organosiloxane latex. This mixed solution was transferred to a separable flask equipped with a condenser and a stirring blade, and mixed and stirred.
After heating at 0 ° C. for 5 hours, the mixture was allowed to stand at 20 ° C., and after 48 hours, the pH of the latex was adjusted to 7.0 with an aqueous sodium hydroxide solution.
The mixture was neutralized to 4 and the polymerization was completed to obtain a silicone rubber latex. The polymerization rate of the obtained polymer was 90.2%, and the average particle size was 0.22 μm. 80 parts of this silicone rubber latex (in terms of solid content) is added to tert-
A mixed solution of 0.05 parts of butyl hydroperoxide and 20 parts of methyl methacrylate was added dropwise at 60 ° C. over 30 minutes, and then kept at 60 ° C. for 2 hours to complete the graft polymerization onto the silicone rubber. The polymerization rate of methyl methacrylate was 96.4%. The measured average particle size of the graft copolymer was 0.24 μm. Next, the resulting graft copolymer latex was added to 600 parts of distilled water containing 5 parts of calcium acetate while stirring to precipitate the resulting copolymer. Then
After separating the precipitated copolymer, washing, dehydration and drying are performed to obtain powdery silicone-based composite particles (C
-1) was obtained.

Example 2 Silicone-based composite particles (C
Production of -2) 50 parts instead of 80 parts of silicone rubber latex, te
Instead of 0.05 parts of rt-butyl hydroperoxide and 20 parts of methyl methacrylate, 0.125 parts each,
Silicone composite particles (C-2) were obtained in the same manner as in Example 1 except that 50 parts were used. Example 3 Production of Silicone Composite Particles (C-3) Instead of 20 parts of methyl methacrylate, 6 parts of acrylonitrile and 14 parts of styrene, and 0.8 part of cumene hydroperoxide instead of 0.05 part of tert-butyl hydroperoxide. Except for using the parts, silicone-based composite particles (C-3) were obtained in the same manner as in Example 1. Example 4 Production of Silicone Composite Particles (C-4) Instead of 80 parts of silicone rubber latex, 50 parts, te
The same procedure as in Example 1 was repeated except that 0.05 parts of rt-butyl hydroperoxide and 20 parts of methyl methacrylate were replaced by 2 parts of cumene hydroperoxide, 15 parts of acrylonitrile and 35 parts of styrene. -4) was obtained.

[0019]

[Table 1]

[Examples 5 to 9] Homopolypropylene pellets (melt flow rate 2)
5 g / 10 min), and hand-blended with the silicone-based composite particles (C-1 to 4) at a ratio shown in Table 2, and then a twin-screw extruder (WERNER & PFLEIDERER).
The melt was kneaded at a barrel temperature of 200 ° C. and a screw rotation speed of 200 rpm using a ZSK30 (manufactured by Sharp Corporation) to form a pellet. Using the obtained pellets, test specimens for measuring various physical properties were prepared with an injection molding machine, and the dynamic friction coefficient, abrasion resistance and molded appearance were evaluated. The cylinder temperature of the injection molding machine is 230
° C and the mold temperature were 35 ° C. Table 2 shows the results. Comparative Example 1 For comparison, a polypropylene resin alone was extruded under the same conditions, test pieces were prepared under the same conditions as in Example 5, and various evaluations were made. [Comparative Example 2] Silicone-based composite particles (C-5) were obtained in the same manner as in Example 1 except that γ-methacryloyloxypropyldimethoxymethylsilane was not used, and a test was performed under the same conditions as in Example 1 using this. Pieces were prepared and various evaluations were made.

[Dynamic coefficient of friction] HE manufactured by Shinto Kagaku Kogyo Co., Ltd.
The dynamic friction coefficient was measured by a surface property tester of IDON-14S. The test was performed under the conditions of a φ10 mm SUS ball indenter, a vertical load of 200 g, and a sliding speed of 100 mm / min. [Abrasion resistance] JIS K7 using Taber abrasion tester
The wear was performed 1000 times with a wear wheel CS10F type, and the amount of wear was determined from the loss mass. [Mold appearance] The appearance of the resin compositions in Examples and Comparative Examples was evaluated by visually observing the degree of gloss unevenness and the degree of planar smoothness on the surface of a plate-like molded product produced by injection molding. The criteria for the determination are as follows. ○: No gloss unevenness, good surface smoothness △: No gloss unevenness, poor surface smoothness, or glossy unevenness, good surface smoothness ×: glossy unevenness, poor surface smoothness

[0022]

[Table 2]

From Table 2, it is clear that the polyolefin resin composition of this example has excellent slidability, is hardly worn, and has a good molded appearance.

[0024]

The silicone-based composite particles which are the slidability modifier of the present invention have extremely good dispersibility in a polyolefin-based resin, and a polyolefin resin composition containing the same has excellent slidability. ing. Further, the means for improving the slidability of a resin by kneading the silicone-based composite particles of the present invention works effectively with a small amount of addition, and does not impair the physical properties of the resin.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) // C10N 40:02 C10N 40:02 F term (reference) 4H104 CA01A CJ07C EA08C PA01 4J002 BB03W BB05W BB12W BB14W BB15W BB17W BB19W BN17XGG GM00 GN00 GQ00 4J027 AF05 BA05 BA07 BA13 CB03 CC02 CD00

Claims (2)

[Claims] 1. One or more vinyls selected from aromatic alkenyl compounds, acrylates, methacrylates and vinyl cyanide compounds with respect to the vinyl polymerizable functional group-containing silicone rubber (B-1). A slidability modifier containing silicone-based composite particles obtained by graft-polymerization of a base monomer (B-2). 2. A resin composition containing 0.1 to 50 parts by mass of silicone composite particles (B) based on 100 parts by mass of polyolefin resin (A), wherein said silicone composite particles (B) are: One or two or more vinyl-based monomers selected from aromatic alkenyl compounds, acrylic esters, methacrylic esters and vinyl cyanide compounds with respect to the vinyl-polymerizable functional group-containing silicone rubber (B-1) ( B-2) a polyolefin resin composition obtained by graft polymerization.