JP2668073B2 - Molding resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molding resin composition, and more particularly to a polyolefin-rubber-modified polystyrene-based resin composition having excellent sheet moldability. 2. Description of the Related Art Conventionally, polyolefin resins such as polypropylene or propylene-ethylene copolymers have been widely used as resin materials for injection molding, film molding, sheet molding, blow molding, etc. because of their low cost and relatively good workability. Although it is used, it has a low rigidity to produce a molded product having a predetermined shape, has poor dimensional accuracy due to shrinkage after molding, and has a sagging phenomenon (draw-down) during vacuum forming. There was a problem that it was not possible to manufacture a molded article of On the other hand, the rubber-modified polystyrene-based resin has been used in various fields such as weak electricity, lighting, vehicles, furniture, and building materials because of its excellent moldability, but it has a drawback that the impact strength is insufficient. Poor solvent resistance,
There is a problem that the use is restricted due to the occurrence of so-called crazing. SUMMARY OF THE INVENTION Therefore, conventionally, a polyolefin-based resin and a rubber-modified polystyrene-based resin, while maintaining the advantages of both, various blend compositions of both polymers to compensate for the drawbacks have been proposed,
Polyolefin resins and rubber-modified polystyrene resins have different chemical structures and are incompatible, so melt-mixing these polymers alone results in phase separation (surface separation).
There is a problem that a resin composition having a practical strength cannot be obtained. The present invention has been made to solve the above-mentioned problems, and can take advantage of the advantages of polyolefin-based resins and rubber-modified polystyrene-based resins, and can make up for the disadvantages, and is excellent in vacuum, pressure forming and extrusion. In addition to being able to obtain a sheet that has sheet formability and is excellent in solvent resistance, impact resistance, heat resistance, and rigidity, the obtained sheet has extremely good drawability and dimensional stability. , The surface of the sheet has good gloss, and the surface roughness can be improved to have a uniform skin. By molding this sheet into a prescribed shape, it is a molded product with excellent dimensional accuracy and appearance. An object of the present invention is to provide a molding resin composition capable of obtaining a resin composition. Means for Solving the Problems In order to achieve the above object, the present invention has a melt index (MFR, 230 ° C.) (hereinafter abbreviated as MFR) of 10 g.
A propylene-ethylene block copolymer (A) having an ethylene content of 1 to 20% by weight for 10 minutes or less,
High-density polyethylene (B) with a melt index (MFI, 190 ° C) (hereinafter abbreviated as MFI) of 1 g / 10 minutes or less, rubber-modified polystyrene-based polymer (G) having a molecular weight of 200,000-400000, and butadiene (Bu) Styrene-butadiene-tapered block copolymer (D) having a content of 30% by weight or less and containing a St.Bu random copolymer portion in the transition part of the block St and the block Bu is blended. The compounding ratio of styrene-butadiene taper block is 100 parts by weight of the total of three components of propylene-ethylene block copolymer (A), high-density polyethylene (B) and rubber-modified polystyrene-based polymer (G). 3 to 30 parts by weight of the copolymer (D), and the above (A) and (B)
In the total of the three components (A) and (G), the sum of the two components (A) and (B) is 30 to 70% by weight, and the component (G) is 70 to 30% by weight. In the total of the two components of B), 70 to 90% by weight of (A) component and 30 of (B) component
The gist is a molding resin composition that is 〜10% by weight. In the above, the MFR of the propylene-ethylene block copolymer (A) is 10 g / 10 minutes or less, preferably 6 g / 10 minutes or less. When the MFR of the copolymer (A) exceeds 10 g / 10 minutes,
In the preheating step during vacuum and pressure forming, the amount of sagging increases, and wrinkles are formed on the formed sheet, and a formed sheet having a uniform thickness cannot be obtained. Moreover, the molding temperature range becomes narrow.
There is no lower limit on the MFR of the block copolymer (A). This is because the propylene oxide-ethylene block copolymer (A) does not cause surface peeling from other components even when it has no fluidity at the time of MFR measurement, so that it can be formed into a sheet. The ethylene content of the block copolymer (A) is 1
-20% by weight, preferably 2-15% by weight. Here, when the ethylene content is less than 1% by weight, the impact resistance of the resin composition is not sufficient, and when it exceeds 20% by weight, the impact resistance is good, but the rigidity and heat resistance of the molded product are not sufficient. It is not preferable. The high-density polyethylene (B) is obtained by a so-called low-pressure method or medium-pressure method, and has at least 0.93
An ethylene homopolymer having a density of 0 g / cc and an MFI (190 ° C.) of less than 1 g / 10 min, or a copolymer containing ethylene as a main component and another α-olefin such as butene. . Here, if the density of the polyethylene (B) is less than 0.930 g / cc, it is not preferable because the strength of the obtained molded article is reduced. When the MFI of the polyethylene (B) exceeds 1 g / 10 minutes, the propylene-ethylene block copolymer (A)
The same problem as in the case (1) occurs, which is not preferable. There is no particular lower limit for the MFI of polyethylene (B),
From the viewpoint of heat resistance, it is preferable to use a high-density polyethylene having an MFI of 0.1 g / 10 minutes or less. The rubber-modified polystyrene-based copolymer (G) is generally called impact-resistant polystyrene, which is a copolymer obtained by polymerizing a styrene monomer in the presence of a rubber-like polymer. It can be produced by a bulk polymerization method or a bulk suspension polymerization method. Such a rubber-modified polystyrene copolymer (G)
Has a molecular weight of 200,000 to 400,000 and a rubber component content of 5 to 9
% By weight. Normal melt index (MF
I, 200 ° C.) 0.1-40 g / 10 min, preferably 1-10 g / 10 min. In the production of the rubber-modified polystyrene-based copolymer (G), when the styrene monomer is polymerized in the presence of the rubber-like polymer, an aromatic monovinyl monomer other than styrene may be optionally used in combination. good. Examples of such aromatic monovinyl monomers include nuclear alkyl-substituted styrenes such as o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene and p-ter-butylstyrene. And α-alkyl-substituted styrenes such as α-methylstyrene and α-methyl-p-methylstyrene. Incidentally, the content of these aromatic monovinyl monomers is 50
% Or less is preferable. As the rubbery polymer, polybutadiene, styrene-
It is a butadiene copolymer or the like, and as the polybutadiene, high cis polybutadiene having a high cis content or o-cis polybutadiene having a low cis content can be used. The rubber-modified polystyrene copolymer (G) has a molecular weight of
It has 200,000 to 400000. Here, if the molecular weight of the rubber-modified polystyrene-based copolymer (G) is less than 200,000, the heat resistance and solvent resistance of the molded product are not sufficient,
It also lacks dimensional stability. When the molecular weight of the rubber-modified polystyrene-based copolymer (G) exceeds 400,000, the compatibility with the polyolefin-based resin is remarkably deteriorated, and the surface layer is easily peeled off. The rubber component content and melt index (MFI, 200 ° C.) of the rubber-modified polystyrene-based copolymer (G) may be in the above-mentioned ordinary ranges. The particle size of the rubber-modified polystyrene-based copolymer (G) is not particularly limited, and usually has an average particle size of 0.30 to 5 µm. Further, the styrene-butadiene tapered block copolymer (D) contains a St.Bu random copolymer portion in a transition portion between block St and block Bu. Here, styrene, vinyltoluene, tertiary butylstyrene, α-
Vinyl aromatic compounds such as styrene and chlorostyrene are used. In addition, a conjugated diene such as butadiene and isoprene is used as a substance constituting the block Bu. It is generally known that the styrene-butadiene tapered block copolymer (D) exhibits a function as a thermoplastic resin when the butadiene component is small, and as a thermoplastic rubber when the conjugated diene component is large. However, in the present invention, the butadiene content is
A so-called thermoplastic resin type styrene-butadiene tapered block copolymer of 30% by weight or less is used. Here, when the butadiene content exceeds 30% by weight,
Since the block copolymer has a high rubber content and exhibits rubber-like elasticity, it is not preferable when molded into a large-sized molding sheet because of its poor rigidity and heat resistance. Also, as described above, it is preferable to use a styrene-butadiene tapered block copolymer, which has a portion where the constituent ratio of each monomer unit of styrene and butadiene changes continuously along the polymer chain. It is a block copolymer (see JP-A-48-48546). Here, the difference between the rubber-modified polystyrene-based copolymer (G) and the styrene-butadiene / tapered block copolymer (D) is that the former is a bulk polymerization method or a bulk suspension method. The latter is clearly different from the one produced by the turbid polymerization method in that the latter is produced by anionic living polymerization. The compounding ratio of each component of the resin composition for molding according to the present invention is as follows. That is, first, with respect to 100 parts by weight of the total of the three components of the propylene-ethylene block copolymer (A), the high-density polyethylene (B), and the rubber-modified polystyrene-based polymer (G), the styrene-butadiene-tapered block copolymer The combined amount (D) is 3 to 30 parts by weight, preferably 8 to 15 parts by weight. Here, generally, the propylene-ethylene block copolymer (A) and the high-density polyethylene (B), that is, the polyolefin-based polymer and the rubber-modified polystyrene-based polymer (G) have almost no compatibility, while styrene-
The butadiene / tapered block copolymer (D) has a high compatibility with the rubber-modified polystyrene-based polymer (G), but has a low compatibility with the polyolefin-based polymers (A) and (B). However, polyolefin polymers (A) and (B)
When the styrene-butadiene / tapered block copolymer (D) is added to the three-component system of the rubber-modified polystyrene-based polymer (G), the compatibility of (G) with (A) and (B) is improved, It has been found that the four components A), (B), (C) and (D) are uniformly mixed. In the above, if the styrene-butadiene / tapered block copolymer (D) is less than 3 parts by weight, the dispersibility of the polyolefin-based polymers (A) and (B) will be insufficient and the polyolefin-based polymers (A) and (B) will be insufficient. Is not preferable because it causes poor dispersion and delamination occurs in the molded article of the resin composition. When the styrene-butadiene tapered block copolymer (D) exceeds 30 parts by weight, the dispersibility of the polyolefin-based polymers (A) and (B) is improved, but the propylene-ethylene block copolymer (A) is improved. The chemical resistance, which is the characteristic of (1), is significantly impaired, and the production cost is high. Next, assuming that the total of the propylene-ethylene block copolymer (A), the high-density polyethylene (B) and the rubber-modified polystyrene-based polymer (G) is 100% by weight,
Of these, the sum of the two components (A) and (B) is 30 to 70% by weight, and the component (G) is 70 to 30% by weight. Here, if the rubber-modified polystyrene-based polymer (G) is less than 30% by weight, a preferable molding temperature range and dimensional stability cannot be obtained during vacuum or pressure molding, and a molded product having a uniform wall thickness cannot be obtained. In addition, there is almost no uniform effect for preventing sagging of the sheet. Further, the extrusion dischargeability is lowered, the sheet is warped or shrunk due to the crystallinity specific to olefin, and the extrusion processability is poor, which is not preferable.
Furthermore, the surface of the sheet becomes rough, the surface gloss decreases,
Not desirable in appearance. 70% by weight of rubber-modified polystyrene polymer (G)
If it exceeds, the impact resistance and chemical resistance of the resin composition will be poor,
Physical properties decrease, such as poor elongation. Finally, in the sum of the two components of the propylene-ethylene block copolymer (A) and the high-density polyethylene (B),
(A) 70-90% by weight, and (B) 30-10% by weight,
Preferably it is 15 to 20% by weight. Here, if the high-density polyethylene (B) exceeds 30% by weight, the heat resistance decreases. If less than 10% by weight,
Impact resistance decreases. When the compounding ratio of the propylene-ethylene block copolymer (A) and the high-density polyethylene (B) is within the above range, the drawability at the time of vacuum forming is improved as the amount of the component (B) increases. However, this alone is not sufficient, and the rubber-modified polystyrene-based polymer (G) is added within the above range in order to further increase drawability. In order to produce the resin composition for molding according to the present invention, the above-mentioned four components (A) to (D) are blended at a predetermined ratio, and the mixture is mixed with a commonly used Hensiel mixer or tumbler. Dry blending may be performed using a suitable mixer, or may be kneaded using a Banbury mixer, a kneader, a screw extruder, or the like, and then temporarily formed into a pellet compound. In this case, generally used in the field of polyolefin resin and rubber modified polystyrene resin, oxygen, heat and light stabilizers, or deterioration inhibitors,
For example, fillers such as talc, silica, charcoal and the like, lubricants, flame retardants, coloring agents and the like may be further added in required amounts. Among the fillers, it is particularly preferable to use talc. The resin composition according to the present invention is usually formed into a sheet by an extrusion molding method. In this case, the sheet can be directly formed into a sheet by a dry blending method or the like, but is usually formed into a sheet by extrusion from a pellet compound. The obtained sheet is further formed into a product having a desired shape by vacuum, pressure forming, press forming or the like. These molding methods are widely known in the field of synthetic resins. In addition, it is of course possible to obtain a molded product by directly introducing the pelletized compound of the resin composition according to the present invention into a predetermined mold without heating the compound into a sheet shape and heating. The resin composition for molding according to the present invention is used for various applications such as electric / electronic devices, automobiles, various mechanical components, interior / exterior parts, housings and the like. Next, an embodiment of the present invention will be described. Example Propylene-ethylene block copolymer (A) having an MFR (230 ° C) of 0.5 g / 10 min and an ethylene content of 5% by weight, and an MFI (190 ° C) of 0.04 g / 10 min. High density polyethylene (B), molecular weight 270,000, rubber component content 8.
Rubber-modified polystyrene homopolymer (G) with 2% by weight, MFI (200 ° C) 2.2g / 10min, and butadiene content 25% by weight
Styrene-Butadiene / Tapered Block Copolymer (D) is mixed in various ratios as shown in the table below to prepare pellet compounds of the resin compositions of Sample Nos. 1 to 14, and these are then added. A sheet having a length of 1000 mm, a width of 500 mm and a thickness of 4 mm was formed by an extrusion sheet forming method.
At this time, for each sample, sheet formability, sheet appearance, solvent resistance, heat resistance, impact resistance and rigidity were evaluated. Next, the sample sheet was cut into a size of 500 mm square, and each sheet piece was subjected to deep drawing at a development rate of 4 times by a vacuum forming method. At this time, the deep drawability of each sample piece and the dimensional stability of the molded product, particularly regarding the external shape, were measured, and the results are shown in the following table. Method of measuring physical properties (i) Sheet moldability was measured by an extrusion molding method. That is, the extruded sheet was evaluated as ○ when no delamination or so-called warpage or sink occurred and had an excellent discharge amount, and was evaluated as x when it was not. (Ii) As for the sheet appearance, the state of surface gloss and surface roughness of each sample sheet was observed. Good surface gloss,
And, those with clean skin were marked with ○, and those with poor skin were marked with ×. (Iii) Regarding the solvent resistance, each material sheet was immersed in acetone (20 ° C. × 3 days) to evaluate the appearance, particularly the occurrence of cracks and the swelling state. (Iv) Heat resistance was measured at a load of 18.6 kg / cm ² based on ASTM D648. (V) Impact resistance was measured by ASTM D256 Izod method (with V notch). (Vi) Stiffness was based on the ASTM D790 method for measuring flexural modulus. (Vii) Deep drawability was evaluated as normal by deep draw forming at a expansion rate of 4 times by the vacuum forming method, whether or not sagging during heating, breakage during forming, and uneven thickness were small. Is indicated by ○, and the other is indicated by ×. (Viii) The dimensional stability of the external shape of the vacuum-formed product is observed by checking whether there is any undulation or warpage.
A normal sample was marked with "O" and a non-normal sample was marked with "x". As is clear from the above table, the sample No.
1, 2, 5, 6, 7, 10, 11 resin compositions have good sheet moldability and sheet appearance, solvent resistance,
It is possible to obtain a sheet excellent in impact resistance, heat resistance and rigidity, the obtained sheet has a good surface gloss, has a clean skin, and has extremely good deep drawability and dimensional stability. A molded product having excellent dimensional accuracy and appearance can be obtained by vacuum forming, and the obtained molded product is a sample of other comparative examples No. 3, 4, 8, 9, 12,
It had significantly better physical properties than the resin compositions of 13 and 14. Effect of the Invention The molding resin composition according to the present invention, as described above,
A propylene-ethylene block copolymer (A) having a melt index (MFR, 230 ° C) of 10 g / 10 minutes or less and an ethylene content of 1 to 20% by weight, and a melt index (MFI, 190 ° C) of 1 g. High-density polyethylene (B) for 10 minutes or less, rubber-modified polystyrene polymer (G) having a molecular weight of 200,000-400000, and butadiene (Bu) content of 30 wt% or less and a transition portion between block St and block Bu To St.
A styrene-butadiene-tapered block copolymer (D) containing a Bu random copolymer portion is blended, and the blending ratio of these is such that the propylene-ethylene block copolymer (A) and the high-density polyethylene ( B) and the sum of the three components of the rubber-modified polystyrene-based polymer (G) is 10
The styrene-butadiene tapered block copolymer (D) is 3 to 30 parts by weight with respect to 0 parts by weight, and in the sum of the three components (A), (B) and (G),
(A) The sum of the two components of (B) is 30 to 70% by weight, and the component (G) is 70 to 30% by weight. Of the total sum of the two components (A) and (B), (A) ) Component is 70 to 90% by weight, and component (B) is 30 to 10% by weight. According to the molding resin composition of the present invention, the polyolefin resin (A) (B) and the rubber-modified polystyrene are used. Resin (G)
Can take advantage of the advantages and make up for the disadvantages, vacuum,
It has good sheet formability in pressure forming and extrusion, and it is possible to obtain not only a sheet with excellent solvent resistance, impact resistance, heat resistance and rigidity, but also the obtained sheet has drawability and size. The stability is extremely good, the surface of the sheet has a good gloss, and the surface roughness can be improved to have a uniform surface. By molding this sheet into a predetermined shape, dimensional accuracy and appearance can be improved. This produces an effect that a molded article having an excellent shape can be obtained.

Claims (1)

(57) [Claims] A propylene-ethylene block copolymer (A) having a melt index (MFR, 230 ° C) of 10 g / 10 minutes or less and an ethylene content of 1 to 20% by weight, and a melt index (MFI, 190 ° C) of 1 g. / 10 minutes or less high-density polyethylene (B), rubber-modified polystyrene-based polymer (G) having a molecular weight of 200,000 to 400,000, and butadiene (Bu) content
Less than 30% by weight and at the transition between block St and block Bu
A styrene-butadiene-tapered block copolymer (D) containing a St.Bu random copolymer portion is blended, and the blending ratio of these is propylene-ethylene block copolymer (A), high density The styrene-butadiene / tapered block copolymer (D) is contained in an amount of 3 to 30 parts by weight based on 100 parts by weight of the total of the three components of the polyethylene (B) and the rubber-modified polystyrene-based polymer (G). ), (B) and (G),
(A) The sum of the two components (B) is 30 to 70% by weight, and the component (G) is 70 to 30% by weight. In the total sum of the two components (A) and (B), (A) ) Component 70-90% by weight, and component (B) 30-10% by weight, a molding resin composition.