JPH0121179B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is based on a soft olefin copolymer rubber and crystalline polypropylene as main components, and has improved injection moldability (flowability), that is, a high melt flow rate index (MFR), and excellent mechanical strength. The present invention relates to a method for producing a resin composition. Soft olefin resin, whose main components are monoolefin copolymer rubber and crystalline polypropylene, has a low specific gravity, excellent heat resistance and weather resistance, and is a relatively inexpensive material. In recent years, it has been rapidly attracting attention for the purpose of reducing weight and cost by replacing ABS resin and RIM urethane parts, improving the lifespan of parts and reducing costs. In particular, replacing large parts such as automobile bumpers and instrument panels with soft olefin resins is a major challenge in the industry, as it can significantly reduce weight and cost. However, soft olefin resins whose main components are monoolefin copolymer rubber and crystalline polypropylene have poor fluidity because they contain rubber components.
It is either impossible to mold large products, or even if it is possible, it is not satisfactory due to problems such as the occurrence of flow marks. The purpose of the present invention is to significantly improve the injection moldability, that is, the fluidity, of conventional soft olefin resins whose main components are monoolefin copolymer rubber and crystalline polypropylene, without compromising mechanical strength. The purpose is to enable the molding of large parts. For example, a method in which conventional olefinic copolymer rubber, crystalline polypropylene, organic peroxide non-crosslinked hydrocarbon rubber, and/or mineral oil is heat treated in the presence of an organic peroxide, and the reaction product is further diluted with olefinic plastic. (Special Publication No. 56-15740,
No. 56-15743) has poor injection moldability and cannot achieve the object of the present invention. Conventional soft olefin resins, which are mainly composed of crystalline polypropylene and monoolefin copolymer rubber, have problems with injection moldability, such as the occurrence of flow marks when large parts are injection molded because they contain rubber components. At present, its uses are largely limited. Therefore, the development of soft olefin resins with excellent injection moldability and mechanical strength has become an important issue in the industry. As a method for improving the injection moldability (flowability) of soft olefin-based resins made of crystalline polypropylene and mono-olefin copolymer rubber, it is simple to use high MFR crystalline polypropylene as a raw material.
Mineral oil-based softeners are added, but when high MFR crystalline polypropylene is used, delamination phenomena may occur on the surface of the molded product, which is thought to be due to a marked difference in fluidity from monoolefin copolymer rubber, and mineral oil softeners may be added. Addition of an oil-based softener has the drawback of significantly impairing heat deformation resistance, and has not been satisfactory. The inventors of the present invention have made intensive studies to improve the injection moldability, which is a drawback of conventional soft olefin resins, and to make it possible to apply this material to large injection molded products. The inventors have discovered that the object can be achieved by employing this method, and have achieved the present invention based on this knowledge. That is, the present invention uses as raw materials 50 to 80 parts by weight of a crystalline propylene homopolymer resin (A) with an MFR of 0.5 to 3.0, preferably 0.5 to 2.0, as measured at 230°C, and 50 to 80 parts by weight of a monoolefin copolymer rubber (B). 20 parts by weight, (A) + (B)
Mineral oil (C) is used in an amount of 5 to 20 parts by weight per 100 parts by weight, and the manufacturing method is as follows: After uniformly melting and mixing all the components (A), (B), and (C) in advance, the granules are mixed. After 0.05 to 0.5% by weight, preferably 0.2 to 0.4% by weight, of organic peroxide is uniformly adhered to the surface of the granules, the organic peroxide is decomposed in an extruder type kneader. This is a continuous granulation method. here,
If a crystalline propylene homopolymer resin with an MFR exceeding 3.0 is used, the mechanical strength will be significantly impaired, and if a crystalline propylene/ethylene copolymer resin is used, the flowability will not be improved and injection moldability will be impaired. I am not satisfied with this point. In the composition ratio of components (A) and (B), if component (A) is less than 50% by weight, flow marks will appear on the injection molded product, and if component (A) exceeds 80% by weight. lacks flexibility and cannot be called a soft olefin resin. Added amount of mineral oil (C) is 20% by weight
If it exceeds this, the molded product will become sticky and its heat deformation resistance will deteriorate. When the amount is less than 5% by weight, the effect of improving injection moldability is not sufficient. When the amount of organic peroxide is less than 0.05% by weight, the fluidity improving effect is not sufficient, and furthermore, the degree of crosslinking of the monoolefin copolymer rubber is low, resulting in poor heat resistance of the product. If it exceeds 0.5% by weight, the MFR of the reaction product increases significantly, making granulation during production difficult. Regarding the manufacturing method, it is impossible to achieve the objective using any method other than the method of the present invention. i.e. ingredients
The composition ratios of (A), (B), (C) and organic peroxide are exactly the same, and one part of component (A) and (B) and (C) are treated with organic peroxide in advance, and the remaining part is treated with organic peroxide. Diluting with component (A) does not improve fluidity and causes flow marks on the molded product. In addition, one part of component (A), (B), and (C) are melted and mixed in advance, and then granulated, and the remaining component (A) is mixed and the organic peroxide is attached at the same time in an extruder. The method of applying peroxide cannot be used because the mechanical strength is significantly lower than that obtained by the method of the present invention. The present invention will be explained in more detail. A predetermined amount of crystalline polypropylene resin (A), monoolefin copolymer rubber (B), and mineral oil are added to a preheated kneading machine such as a roll mill, Banbury mixer, or pressure kneader.
Add (C) and knead for 5 to 10 minutes. The uniformly melted and mixed mixture is taken out, cooled and solidified using a roll mill and formed into a sheet, and this sheet is made into pellets using a cube pelletizer. Next, the pellets and a predetermined amount of organic peroxide are placed in a V-type blender, tumbler, or Henschel mixer, and mixed until the organic peroxide is uniformly attached to the surface of the pellets. The mixture is kneaded in an ordinary extruder heated to about 170 to 250°C to decompose the organic peroxide, and at the same time, the reaction product flowing out from the die is cooled and solidified to continuously produce the mixture. By granulating, a soft olefin resin composition having excellent injection moldability and mechanical strength can be obtained.
In the above process, at any stage various pigments,
Heat stabilizers, weather stabilizers, and fillers may also be added. Next, components (A), (B), (C) and organic peroxide used in the present invention will be explained. Component (A) is highly crystalline isotactic or syndiotactic polypropylene obtained by polymerizing propylene using a Ziegler-Natsuta catalyst, and has an MFR of 0.5 to 3.0 as measured at 230°C. component
(B) is an essentially amorphous random copolymer of two or more types of monoolefins and at least one type of polyene that can be copolymerized with them using a Ziegler-Nack catalyst consisting of a combination of a vanadium compound and an aluminum compound. It is a copolymer. In general, ethylene/propylene/dicyclopentadiene copolymer rubber, ethylene/propylene/ethylidenenorbornene copolymer rubber, and ethylene/propylene/1,4-hexadiene copolymer rubber are available and preferably used. Component (c) is an aromatic, naphthenic, or paraffinic mineral oil commonly used as a rubber processing aid or softener, and may be a mixture thereof. Examples of organic peroxides include 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, di-t-butylperoxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, di-t-butylperoxydiisopropylbenzene, dicumyl peroxide, t-butylperoxybenzoate, 1,1-bis(t-butylperoxy)
-3,3,5-trimethylcyclohexane, 2,
Examples include 4-dichlorobenzoyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide, and more preferably a high-temperature decomposition type is selectively used. Next, to describe the effects of the present invention, Examples 1 to 2 and Comparative Examples 1 to 5 below show the properties of reaction products obtained by the method of the present invention by changing the type of crystalline polypropylene resin. However, for resins other than the present invention, i.e., propylene homopolymer resins with high MFR, the elongation at break (E _B ) of the product is 50 to 70%, and the 530 ~
570% (Examples 1 and 2 and Comparative Examples 1 and 2), and when crystalline propylene/ethylene copolymer resin was used instead of crystalline polypropylene resin, the break point of the product Extremely low elongation and stiffness (Comparative Examples 3 and 4), fluidity (MFR),
Molding appearance (flow marks) is poor. (Comparative Example 5). Comparative Examples 6 and 7 show the properties of products obtained by a method different from the production method of the present invention.
A product obtained by reacting a part of crystalline polypropylene resin, monoolefin copolymer rubber, and mineral oil with an organic peroxide in a Banbury mixer, and diluting and mixing the remaining crystalline polypropylene resin. Although the composition had excellent mechanical strength, the injection molded appearance was extremely poor (Comparative Example 6). In addition, a part of the crystalline polypropylene resin, monoolefin copolymer rubber, and mineral oil are melt-mixed in advance in a Banbury mixer to form square pellets, and at the same time, the remaining crystalline polypropylene resin is attached to the square pellets. The elongation at break and the injection molded appearance of the product obtained by dry-blending the mixture in an extruder are significantly worse than those of the present invention (Comparative Example 7). Next, the present invention will be explained in more detail with reference to Examples. Details of each component used in the following Examples and Comparative Examples are as follows. (1) Crystalline polypropylene resin PP(1)...(MFR, 1.0, density: 0.90, propylene homopolymer) PP(2)...(MFR; 0.6, density: 0.90, propylene homopolymer) PP(3)... ...(MFR; 11.0, density: 0.90, propylene homopolymer) PP(4)...(MFR; 5.0, density: 0.90, propylene homopolymer) PP(5)...(MFR; 6.5, density: 0.90, propylene PP(6)...(MFR; 2.7, density: 0.90, propylene/ethylene block polymer) PP(7)...(MFR; 1.8, density: 0.90, propylene/ethylene block polymer) (2) Ethylene・Propylene ethylidene norbornene copolymer rubber (EPDM) EP(1)...(Propylene content: 28wt%, iodine value: 15, extension oil: paraffin oil 50PHR,
ML ₁₊₄ 100=50) EP(2)...(Propylene content; 43wt%, iodine value; 15, ML ₁₊₄ 100=105) EP(3)...(Propylene content; 43wt%, iodine value; 26, ML ₁₊₄ 100=83) EP(4)...(Propylene content; 28wt%, iodine value; 15, ML ₁₊₄ 100=90) (3) Mineral oil Oil (1)...Paraffin-based process Oil (specific gravity: 0.8971, kinematic viscosity: 194cst (37.8℃), viscosity index: 92.0) (4) Organic peroxide PO(1)...2,5dimethyl-2,5-di(t-
butylperoxy)hexane Examples 1 to 5, Comparative Examples 1 to 5 70 parts by weight of crystalline polypropylene resin (type: 1
(shown in the table), 30 parts by weight of ethylene propylene/ethylidene norbornene copolymer rubber (types are shown in Table 1), and 15 parts by weight of mineral oil (Banbury mixer with internal volume 4 (manufactured by Godo Heavy Industries) preheated to 110°C)
The mixture was mixed for 5 minutes at a rotor speed of 60 rpm.
The mixture was taken out and rolled into a sheet with a thickness of about 2 mm using a 10-inch roll. This sheet was diced into pellets of about 2 mm ³ using a pelletizer. This pellet
100 parts by weight and 0.35 parts by weight of organic peroxide PO(1) were added to a tumbler mixer and mixed for 5 minutes to uniformly adhere the organic peroxide to the pellet surface.
Next, the organic peroxide-adhered pellets were kneaded and granulated using a 55φ vented extruder (L/D=28, full-flight screw) with a cylinder temperature of 200°C. (The above manufacturing method is referred to as manufacturing method A.) The obtained product is molded using an injection molding machine (3.5 oz, molding temperature 240°C).
℃) into a test piece of 100 x 100 x 2 mm and subjected to physical property evaluation. The evaluation results are shown in Table 1. Comparative Example 6 Using the same raw materials as in Example 5, a softened olefin resin was produced according to the following procedure. That is, 40 parts by weight of PP (1), 60 parts by weight of EP (4), and 30 parts by weight of Or (1) were kneaded for 3 minutes in a Banbury mixer preheated to 110°C, and then 0.62 parts by weight of PO (1) was mixed. % was added and kneading was continued for an additional 7 minutes until 100% of the PO was added. The product taken out from the Banbury mixer was rolled into a sheet with a thickness of about 2 mm using a 10-inch roll, and into pellets with a size of about 2 mm ₃ using a cube pelletizer. 56.5 parts by weight of the pellets and 43.5 parts by weight of PP(1) were put into a tumbler mixer, dry blended for 5 minutes, and then kneaded and granulated using a 55φ vented extruder. (The above manufacturing method is referred to as manufacturing method B.) Physical property evaluation is Examples 1 to 5 and Comparative Examples 1 to 5.
It was carried out using the same procedure. The physical property evaluation results are shown in Table 2. Comparative Example 7 After kneading 40 parts by weight of PP (1), 60 parts by weight of EP (4), and 30 parts by weight of oil (1) in a Banbury mixer preheated to 110°C for 5 minutes, the mixture was taken out and 10 parts by weight were mixed. It was made into a sheet using an inch roll and made into pellets using a cube cutter. This pellet
56.5 parts by weight, 43.5 parts by weight of PP(1), and 0.35 parts by weight of PO(1) were put into a tumbler mixer, and mixed for 5 minutes to uniformly adhere PO. PO adhesion mixture
The mixture was kneaded and granulated using a 55φ vented extruder.
(The above manufacturing method is referred to as manufacturing method C.) The physical property evaluation results are shown in Table 2. The final products of Example 5 and Comparative Examples 6 to 7 shown in Table 2 have exactly the same raw material components and composition ratios. Examples 6 to 11 Table 3 shows examples where PP (1), EP (4), oil (1), and PO (1) are used as raw materials, and the composition ratio of the raw materials is changed according to manufacturing method A. Ta. The test methods for the physical property evaluation items shown in Tables 1 to 3 are listed below. (1) MFR; ASTM D1238 (230℃) (2) Shore D hardness; ASTM D2240 (3) Flexural modulus; ASTM D790 (4) T _B (strength at break); JISK6301 (5) E _B (elongation at break) (6) Flow mark: Visually judge injection molded plate of 100 x 100 x 2 mm. (None; 〇, Slightly present; △, Significantly; ×) (7) Stickiness: No resistance when pulling apart injection molded plates of 100 x 100 x 2 mm after stacking them; 〇, Some resistance; , Severely sticky; ×.

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【table】

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[Table] Comparative Examples 8 and 9 In Example 5, PP (1), EP (4), oil (1),
When PO(1) is added all at once (Comparative Example 8), PP(1) and
Table 4 shows the evaluation results of the physical properties of the product obtained when EP (4) was kneaded and then oil (1) and PO (1) were added and kneaded (Comparative Example 9).

【table】

[Table] Compared to Example 5, Comparative Example 8 has T _B ,
A decrease in E _B and the occurrence of flow marks were observed, and the mechanical properties and workability were poor. Further, when oil is added afterward as in Comparative Example 9, it is extremely difficult to get caught in the extruder, resulting in extremely poor workability. Furthermore, T _B ,
E _B 's mechanical properties deteriorated and flow marks and stickiness were observed.

Claims (1)

[Claims] 1 50 to 80 parts by weight of a crystalline propylene homopolymer resin (A) with a melt flow rate index (MFR) of 0.5 to 3.0 measured at 230°C, and 50 to 20 parts by weight of monoolefin copolymer rubber (B). Weight part, (A) + (B) 100
After uniformly melting and mixing 5 to 20 parts by weight of mineral oil (C), the mixture is granulated and coated on the surface of the granules.
Injection moldability (fluidity) characterized by uniformly depositing 0.05 to 0.5 parts by weight of an organic peroxide and continuously granulating it in an extruder-type kneader while allowing the organic peroxide to act. , a method for producing a soft polyolefin resin composition with excellent mechanical strength.