JPS58153643A - Multilayer polypropylene sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer polypropylene sheet for pressure forming and vacuum forming that has excellent rigidity and gloss.

Currently, a method of forming a plastic sheet with a thickness of 1 to 4 ms into a desired shape by air pressure forming or vacuum forming is widely used for parts of automobiles, electrical appliances, office machines, and the like. Conventionally, plastic materials used in such molding methods include polyvinyl chloride, polystyrene, and AB8.
and polypropylene, but each has advantages and disadvantages, and the reality is that their use is limited depending on their intended use. For example, the problem of waste pollution with polyvinyl chloride is deeply debated, and the use of polystyrene is limited due to its weak chemical resistance.

Furthermore, ABS has not become widely popular due to its high price. Among these materials, polypropylene has the advantages of fewer waste pollution problems, excellent heat resistance and impact strength, and low price.
Since it has disadvantages such as lower rigidity and inferior surface gloss compared to ABS and polystyrene, attempts have been made to improve these disadvantages. For example, in order to increase rigidity, it is often adopted to mix inorganic fillers such as talc and calcium carbonate, but on the contrary, the gloss is significantly reduced and it cannot be used for applications where surface appearance is important.

The inventors of the present invention have arrived at the present invention as a result of intensive studies aimed at obtaining a sheet with excellent gloss and rigidity while taking advantage of the properties of polypropylene sheets.

That is, the present invention contains talc and/or calcium carbonate having an average particle diameter of 2 μm or less, and a melt flow index (hereinafter abbreviated as MFI) of 0.1 to 10 g.
/10 minutes with polypropylene resin as the main layer, MFI
This sheet is made by coating the main layer with a polypropylene resin having a weight of 1.5 to 5 g/10 minutes to a thickness of 5 to 20 inches.

The sheet of the present invention has significantly superior gloss and rigidity compared to conventional polypropylene sheets for air pressure forming and vacuum forming. In the case of conventional polypropylene sheets, even if the sheet has good gloss, the gloss of the molded product obtained by pressure forming and vacuum forming is poor due to so-called gloss return. On the other hand, the sheet according to the present invention is characterized in that the gloss of the molded product is also extremely good.

The polypropylene resin used to form the main layer in the present invention contains 5 to 30% by weight of talc and/or calcium carbonate having an average particle size of 2 μm or less. If the average particle size exceeds 2 μ, even if the surface is coated with a polypropylene resin having an MFI of 1.5 to 5 g/10 minutes, only a sheet with poor gloss will be obtained, and the resulting sheet will have low impact strength.

The inorganic filler to be added may be talc or calcium carbonate, and both may be used in combination. By including 5 to 50% by weight of talc and/or calcium carbonate having the above particle size, the rigidity of the resulting multilayer polypropylene sheet is greatly improved. If the amount added is less than 5% by weight, the rigidity will not be improved sufficiently, while if it exceeds 30% by weight, the impact strength will decrease and the material will become brittle at low temperatures. be done. Inorganic fillers other than talc and calcium carbonate may not improve rigidity sufficiently, the resulting sheet may have poor gloss, or may be difficult to air-form.

It has disadvantages such as poor vacuum formability and is therefore unsuitable.

Examples of the polypropylene resin used to form the main layer in the present invention include propylene homopolymers, copolymers of propylene and other α-olefins, and among others, propylene and ethylene are preferred from the viewpoint of impact strength. The block copolymer may contain a small amount of high-density polyethylene, low-density polyethylene, EPR, etc. The MFI of polypropylene 1★ soot is 0°1~1.09710
minutes are used, which means an MFI range suitable for air forming and vacuum forming.

In the present invention, the MFI of the polypropylene resin coating the main layer is 1.5 to 5 g/10 min. This causes a so-called gloss return phenomenon, and the gloss of the molded product is not good.

If the MFI is larger than 5y/10 minutes, the sheet becomes sticky and adheres to the plug during thermoforming of the sheet, resulting in poor molding.

As the polypropylene resin to be coated on the surface, a propylene homopolymer, a copolymer of propylene and other α-olefins, for example a copolymer of propylene and ethylene, etc. are used.

It is desirable to use a material containing a transparent nucleating agent such as sodium benzoate, since it has the effect of improving surface gloss.

The thickness of the layer coated on the surface is 5 to 20% of the thickness of the main layer.
If this thickness is less than 5 mm, the gloss of the entire sheet will not be improved much even if it is coated with a resin having excellent gloss.

On the other hand, if it exceeds 20%, a sagging phenomenon occurs during thermoforming of the sheet, resulting in a decrease in thermoformability and product quality, making it unsuitable for use in pressure forming and vacuum forming.

There are no particular restrictions on the method for manufacturing the laminated sheet, but there are methods such as co-extrusion using a feed block or multilayer die, or a method in which a thin sheet for surface coating is made in advance and the main layer is extruded into a sheet. A heat lamination method is used to form a multilayer polypropylene sheet having a thickness of usually 1 to 4 tnm.

The laminated sheet produced in this way has excellent surface gloss, is strong and has good elasticity, and is suitable for pressure forming and vacuum forming, and the surface gloss of the thermoformed product is also extremely good. Applications for such multilayer polypropylene sheets include cosmetic cases, office machinery, housings,
Suitable for parts that require aesthetic appearance, such as refrigerator door backs, bathtubs, washroom shelves, etc.

The present invention will be further explained below with reference to Examples.

Example 1 A propylene-ethylene block copolymer manufactured by Mitsui Toatsu Chemical Co., Ltd. containing 20 weights of calcium carbonate with an average particle size of 11μ as the main layer resin (ethylene content 7% by weight, 11i1F
I was 0.5.9/min). A propylene homopolymer having an MFI of 4.0 p/10 minutes was used as the resin for surface lamination.

First, 60% of the above propylene homopolymer for surface coating was added.
1! The product was extruded using a Wl extruder at an extrusion temperature of 240°C to form a sheet with a thickness of 150°C using a T-die air knife method and a chill roll temperature of 80°C.

On the other hand, the resin for the main layer was extruded using a 90°C extruder at an extrusion temperature of 2
Sheet molding was performed using a T-die and three-roll method at 50°0. At this time, at the inlet of the six rolls,
By merging 50μ thick sheets and thermally laminating them to the main layer using roll heat pressure, the total thickness is 2.
．． A laminated sheet of 0 sheets was obtained.

In this case, the ratio of the thickness of the covering layer to the main layer is 8
It is 1ch.

The gloss and bending line incidence angle of the thus obtained sheet were measured at 60 degrees. Measurement of flexural modulus is ASTM-
It was carried out according to the method of D-790-63.

The resulting sheet was molded into a container with a tow angle of 500 mm and a depth of 300 mm using a vacuum forming machine manufactured by Asano Research Institute Co., Ltd., and the thickness of a part of the corner was measured to examine suitability for vacuum forming. The results are shown in Table 1.

It was confirmed that the sheet according to this example was excellent in gloss and rigidity, and had good vacuum forming suitability and gloss of the molded product.

Example 2 A multilayer sheet was obtained in the same manner as in Example 1, except that a propylene-ethylene block copolymer containing 25% by weight of talc with an average particle diameter of 17 μm was used as the resin for the main layer. The obtained sheet had excellent gloss and rigidity, and the physical properties and moldability evaluation results are shown in Table 1.

Example 6 A multilayer sheet was obtained in the same manner as in Example 1, except that a propylene-ethylene block copolymer containing 15% by weight of talc with an average particle size of 1.7 μm was used as the resin for the main layer. The physical properties and moldability evaluation results of the sheet are shown in Table 1.

Example 4 A propylene-ethylene block copolymer (ethylene content: 5% by weight) containing 27% by weight of calcium carbonate with an average particle size of 0.1μ and having an MFI of 0.2g/10 minutes was used as the resin for the main layer. MFI is 4,0g710 as surface coating layer
A multilayer sheet with a thickness of 2.0 μm was obtained in the same manner as in Example 1 except that a 200 μm thick sheet made of a propylene homopolymer of 1.0 μm was used. The physical properties and moldability of this product were evaluated and shown in Table 1.

Example 5 In Example 4, the surface coating layer had an MFI of 2.597.
A multilayer sheet was obtained in the same manner except that a 10-minute homopolymer was used. Table 1 shows the physical properties and moldability.

Comparative Example 1 A 2.0-thick sheet was molded using only the main layer in Example 1 without forming a surface coating layer, and its gloss, flexural modulus, and vacuum formability were evaluated. Although the sheet surface in this case was relatively good, the gloss of the molded product after vacuum forming was significantly reduced.

Comparative Example 2 A multilayer sheet was obtained in the same manner as in Example 2 except that a propylene-ethylene block copolymer containing 25% by weight of talc with an average particle size of 6 μm was used as the resin for the main layer. The effect of improving gloss was small (no difference from the conventional one).

Comparative Example 3 A multilayer sheet was obtained in the same manner as in Example 1 except that the thickness of the surface coating layer was 400 μm and the total sheet thickness was 2.0 ms. In this case, the ratio of the thickness of the cover layer to the main layer is 25 inches. Although the surface gloss was good, the sheet sagged during vacuum forming, and some of the corners were thinner, making it impossible to commercialize the product.

Comparative Example 4 In Example 1, the resin for the surface coating layer had an MFI of 1.
A multilayer sheet was obtained in the same manner except that 0g/10min of propylene homopolymer was used. Although the surface gloss of the sheet was good, the gloss of the molded product after vacuum forming was poor.

Claims (1)

[Claims] Contains 5 to 30% by weight of talc and/or calcium carbonate with an average particle size of 2μ or less, and has a melt flow index of 0.
．． The main layer is polypropylene resin with a melt flow index of 1.5 to 5 p.
/10 minutes multilayer polypropylene sheet for polypropylene resin vacuum forming.