JP3006897B2 - Thermoforming sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoforming sheet capable of obtaining a thermoformed product having a good appearance without excessive drawdown and tearing of the sheet in vacuum and compressed air thermoforming. It is suitably used for automobile parts and building materials.

[0002]

2. Description of the Related Art Conventionally, thermoformed products have been obtained from various plastic sheets. For example, in order to impart rigidity, a sheet for thermoforming using a resin composition in which an inorganic filler, wood powder, and the like are blended with a polypropylene resin, or a sheet having two surfaces, a thermoplastic elastomer layer and a polypropylene resin layer, has a soft surface. A method of obtaining a thermoformed product using a thermoforming sheet having properties has been implemented.

[0003]

When a resin composition in which an inorganic filler is blended with a polypropylene resin is thermoformed, rigidity can be expected, but the flexibility of the surface layer and the pattern (texture) on the surface of a mold used in thermoforming can be expected. ) Often, drawbacks arise in providing transferability.

[0004] Therefore, in order to impart flexibility and texture transferability of the surface layer, there is often seen a case where a two-layer sheet provided with a thermoplastic elastomer layer on the textured surface is used.

However, thermoplastic elastomers have a lower melt tension than polypropylene resins,
The drawdown resistance of the two-layer sheet is reduced, so that a thermoformed product having a uniform thickness cannot be obtained, or in a severe case, there is a problem that the sheet is broken at the time of heating.

The present invention solves the above-mentioned problems, increases the drawdown resistance of the thermoplastic resin layer, and enables the use of a two-layer sheet with a thermoplastic elastomer layer to prevent the sheet from being torn at the time of thermoforming. The purpose is to prevent the thickness of the molded product from becoming uneven.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a thermoplastic resin layer comprising (A) a propylene-ethylene block copolymer, (B) a high-density polyethylene, and (C) an inorganic filler. And (D) a layer formed of a polyolefin-based thermoplastic elastomer, wherein the ratio of the content of (A) the propylene-ethylene block copolymer to the content of (B) the high-density polyethylene [ (A) / (B)] is 6.0 to 1.5 (weight ratio), (C) the content of the inorganic filler in the thermoplastic resin layer is 20 to 40% by weight, and (B) The above object can be achieved by a thermoforming sheet of high-density polyethylene having an apparent viscosity of 8 × 10 ^{4 to} 3 × 10 ⁵ (poise) at 230 ° C. and a shear rate of 10 (sec ⁻¹ ). To complete the present invention. Has come to fruition.

The composition ratio of the thermoplastic resin layer used in the present invention is as follows: (A) the ratio of the amount of the propylene-ethylene block copolymer and (B) the amount of the high-density polyethylene [(A)
/ (B)] in the range of 6.0 to 1.5 (weight ratio), preferably 5.0 to 2.0.

If the ratio [(A) / (B)] exceeds 6.0, the drawdown resistance during thermoforming is poor, resulting in a molded article with uneven thickness, which is less effective. On the other hand, the ratio [(A) / (B)]
Is less than 1.5, the melt viscosity of the polyolefin-based resin layer becomes too high, and when a thermoforming sheet is formed, a sheet having a uniform thickness may not be obtained continuously. Further, the rigidity of the thermoformed product is reduced.

Further, the content of the inorganic filler (C) in the thermoplastic resin layer is 20 to 40% by weight, preferably 25 to 35% by weight.

When the content of the inorganic filler (C) in the polyolefin resin layer exceeds 40% by weight, the impact resistance of the sheet decreases, and when it is less than 20% by weight, the rigidity of the sheet decreases.

The propylene-ethylene block copolymer (A) used in the present invention contains propylene as a main component,
It is a polymer obtained by block copolymerizing propylene and a small amount (usually 20% by weight or less) of ethylene, and is not particularly limited. The content of the propylene rubber component in the block copolymer is 10 to 20% by weight. Are preferred. Melt flow rate (JIS K7210, 230 ° C, 2.1
6kg load. Hereinafter, it may be referred to as MFR. )
Preferred is 2 to 20 g / 10 min.

The high-density polyethylene (B) used in the present invention may be ethylene homopolymer or a small amount of ethylene-based carbon having a carbon number of 8 or less, which is obtained by polymerization using a known medium-to-low pressure polyethylene production facility. Is used.

The apparent viscosity of the high-density polyethylene is:
8 × 10 ⁴ when the shear rate is 10 (sec ⁻¹ ) at 230 ° C.
3 × 10 ⁵ (poise), preferably 1 × 10 ⁵ to
It is 2 × 10 ⁵ .

The apparent viscosity of the high-density polyethylene is 8
When it is less than × 10 ⁴ (poise), a problem of tearing occurs during thermoforming. On the other hand, when the apparent viscosity of the high-density polyethylene exceeds 3 × 10 ⁵ (poise), the state of melting and dispersion with polypropylene becomes poor, and the sheet appearance may be poor.

With respect to the above-described high-density polyethylene, the temperature dependence of the melt tension is smaller than that of polypropylene.
It was found that the molding temperature range during thermoforming could be widened.
Melt tension has a certain proportional relationship with melt viscosity, and the polyethylene used in the present invention has a shear rate of 10% at 230 ° C.
(sec ^-1 ), 8 × 10 ⁴ (poise) to 3 × 10 ⁵ (poi
se), the thermoplastic elastomer sheet and 2
Even if the layers are thermoformed, a molded article having good appearance without breakage due to heat can be obtained.

Further, in the high-density polyethylene, usually,
The density (JIS K7210, measured at 190 ° C. under a load of 2.16 kg) must be 0.935 g / cc or more.
Those having 0.940 or more are more preferably used. If the density is less than 0.935, the rigidity of the sheet will be insufficient.

Examples of the inorganic filler (C) used in the present invention include talc, calcium carbonate, mica and the like. Finer grain size is better to increase rigidity, but 50%
If the particle size is defined as the central particle size, the range of 1 to 10 μm is appropriate, and preferably 3 to 5 μm. These amounts and types may be appropriately selected in consideration of necessary rigidity, cost, and the like.

In the present invention, (D) a polyolefin-based thermoplastic elastomer is indispensable as the thermoplastic elastomer in view of the adhesiveness of two layers and the transferability of the grain.

The (D) polyolefin-based thermoplastic elastomer which can be used in the present invention is an ethylene-propylene rubber (hereinafter sometimes referred to as EPR) and / or a terpolymer of ethylene-propylene-diene monomer (hereinafter referred to as EPDM). A) a composition of the EPR and / or the EPDM and a polypropylene resin;
It is a partially crosslinked product of the EPR and / or the EPDM, or a composition of the partially crosslinked product and the polypropylene resin.
Is more preferable.

The polypropylene resin used for the polyolefin thermoplastic elastomer (D), which is a component of the present invention, includes a well-known propylene homopolymer and a random copolymer of propylene and a small amount (usually 10% by weight or less) of ethylene. Coalescing or propylene and ethylene block copolymers.

The above-mentioned EPR is not particularly limited, but has a low crystallinity having an ethylene copolymerization ratio of 60 to 80 mol% and an ethylenic crystallinity by X-ray of about 4 to 20%, and MFR (JIS K7210, condition 14)
Is preferably about 0.05 to 5.0 g / 10 minutes.

Similarly, the above EPDM is not particularly limited, but the copolymerization ratio of ethylene is 60 to 80 mol.
%, Copolymerization ratio of diene monomer is 0.3 to 10 mol%
Those having a degree of value are preferably used.

The above diene monomer is a non-conjugated diene monomer, and various types can be used. Specific examples thereof include dicyclopentadiene, ethylidene norbornene, and hexadiene.

When the polyolefin-based thermoplastic elastomer contains a partially crosslinked product of EPR and / or EPDM, the gel fraction of the partially crosslinked product is 15 to 40% by weight when extracted at the xylene boiling point for 6 hours. Are preferred.

The composition ratio of the total amount of EPR and EPDM to the polyolefin-based thermoplastic elastomer is preferably about 10 to 60% by weight.

Some or all of the components (A), (B), (C) and (D) of the thermoforming sheet according to the present invention may be used, if necessary, as long as the properties of the present invention are not significantly impaired. , An antioxidant, an antistatic agent, a coloring agent, a flame retardant, and the like.

[0028]

The present invention will be described in more detail with reference to the following examples. Example 1 A propylene-ethylene block copolymer having an MFR of 4 and a capillary rheometer at 230 ° C. having an apparent viscosity at a shear rate of 10 (sec ⁻¹ ) of 1.2 × 10 ⁵ (p
oise) and 5% by weight of talc and melt extruded from a T-die having a die width of 500 mm and a lip of 3.5 mm using a 65 mmφ extruder. It was laminated with a 5 mm thick polyolefin-based thermoplastic elastomer sheet by an extrusion lamination method to obtain a 3.5 mm thick two-layer sheet. Examples of the polyolefin-based thermoplastic elastomer include an ethylene copolymerization ratio of 65 mol%, an X-ray ethylenic crystallinity of 5%, an EPR of 0.9 g / 10 min, an ethylene copolymerization ratio of 70 mol%, and ethylidene norbornene. Is a polypropylene-based thermoplastic elastomer obtained by partially cross-linking a composition of EPDM and a propylene homopolymer having a copolymerization ratio of 0.4 mol%, and a total ratio of EPR and EPDM to the elastomer is 22% by weight, and propylene alone is used. The polymer used had a polymer content of 78% by weight and a gel content of 20% by weight after extraction for 6 hours at the xylene boiling point. The sheet was preformed at 105 ° C. and then thermoformed. Table 1 shows the test results of the drawdown resistance during thermoforming, the appearance and rigidity of the molded article after thermoforming.

[0029]

[Table 1]

As a result, a thermoformed product having good drawdown resistance during thermoforming and having very good appearance and rigidity could be obtained.

Example 2 In Example 1, the mixing ratio of the propylene-ethylene block copolymer to polyethylene was 3.5: 1, and the apparent viscosity of the polyethylene was 2.0 × 10 ⁵ (poise). Were molded under the same conditions as in Example 1 to obtain a thermoformed product. The drawdown resistance during thermoforming was very good. In addition, a thermoformed product having good appearance and rigidity was obtained.

Example 3 A thermoformed product was obtained under the same conditions as in Example 1 except that the mixing ratio of the propylene-ethylene block copolymer and polyethylene was changed to 3.5: 1. The drawdown resistance during thermoforming was good, and the appearance was very good and the rigidity was good.

Comparative Example 1 The apparent viscosity of polyethylene was 3.2 × 10 ⁴ (poise)
A thermoformed product was obtained under the same conditions as in Example 1 except that the temperature was low. The drawdown resistance during thermoforming was particularly poor, wrinkles occurred on the surface of the thermoformed product, and the appearance was poor.

Comparative Example 2 A thermoformed product was obtained under the same conditions as in Example 1 except that the mixing ratio of the propylene-ethylene block copolymer and polyethylene was 1: 1. The rigidity at the time of the thermoforming was particularly poor, and the appearance was also wavy and inferior.

Comparative Example 3 A thermoformed product was obtained under the same conditions as in Example 1 except that the amount of talc added was 10% by weight. The rigidity of the thermoformed product was inferior.

Comparative Example 4 A thermoformed product was obtained under the same conditions as in Example 1 except that the mixing ratio of the propylene-ethylene block copolymer and polyethylene was 7: 1. The drawdown resistance during thermoforming was poor, and the appearance of the resulting thermoformed product was also poor.

[0037]

The sheet for thermoforming according to the present invention is excellent in melt tension, and solves the problems of sheet breakage due to drawdown and uneven thickness during thermoforming without impairing the grain transferability of the thermoplastic elastomer layer. Thus, a thermoformed product having excellent rigidity and good appearance can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-167048 (JP, A) JP-A-63-37936 (JP, A) JP-A-59-165654 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 51/00-51/46

Claims (1)

(57) [Claims] 1. A thermoplastic resin layer comprising (A) a propylene-ethylene block copolymer, (B) a high-density polyethylene, and (C) an inorganic filler, and (D) a layer comprising a polyolefin-based thermoplastic elastomer. A thermoforming sheet comprising: (A) a ratio of the content of the propylene-ethylene block copolymer to the content of the (B) high-density polyethylene [(A) / (B)] of 6.0 to 1.0. 5 (weight ratio), (C) the content of the inorganic filler in the thermoplastic resin layer is 20 to 40% by weight, and (B) a high-density polyethylene having a shear rate of 10 (se) at 230 ° C.
The apparent viscosity in c ^-1 ) is 8 × 10 ^{4 to} 3 × 10 ⁵
(poise) thermoforming sheet.