JPH0718109A - Polypropylene-based resin foam and polypropylene-based resin foam laminate - Google Patents

Abstract

PURPOSE:To obtain a polypropylene-based resin foam and a polypropylene-based resin foam laminate not causing draw down and abnormal surface waviness phenomena during vacuum molding, useful as a material for providing vacuum molded articles having excellent appearance state free from wrinkle and unevenness. CONSTITUTION:A polypropylene-based resin composition comprising 70 pts.wt. of a polypropylene-ethylene random copolymer, 30 pts.wt. of a straight-chain polyethylene, 12 pts.wt. of azodicarboxylic acid amide and 2 pts.wt. of divinylbenzene is extruded from an extruder to give an unexpanded sheet. This unexpanded sheet is irradiated with ionizing radiation to give an unexpanded sheet (40% cross-linking degree). This cross-linked unexpanded sheet is heated at 220 deg.C by a foaming machine, expanded at 0.1kg/cm<2> tension in the longitudinal direction, simultaneously drawn at 0.05kg/cm<2> tension in the lateral direction and cooled to give a polypropylene-based foam having 25 times expansion ratio and 3mm thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a vehicle interior material, for example,
Polypropylene resin foam and polypropylene resin foam with excellent vacuum moldability, which are molded by vacuum molding methods such as ceiling materials, doors, instrument panels, console boxes, rear wheel house covers, luggage house covers, trunk loam covers, etc. The present invention relates to a laminated body product.

[0002]

2. Description of the Related Art When a polypropylene resin foam sheet is manufactured by vacuum forming, the sheet is preheated to 130 to 200 ° C. by a heater or the like. At this time, the polypropylene-based resin foam sheet thermally expands and causes a drooping phenomenon (drawdown), and since the end portion of the sheet is fixed, an abnormal waviness phenomenon of the sheet occurs in some cases. If vacuum forming is performed in a state where this phenomenon is large, there is a problem that after the forming, the remaining wrinkles of the sheet remain on the forming die or the base material, and the obtained product has a poor appearance.

In order to solve this problem, for example, as described in JP-A-4-290731, a polypropylene resin composition containing 50% by weight or more of a polypropylene resin in a polyolefin resin is foamed to form a polypropylene resin. In the method for producing a foamed sheet, the polypropylene-based resin composition is foamed and cooled in a state where tension is constantly applied, so that the thermal shrinkage in the length direction is 10% or more and the thermal expansion coefficient in the thickness direction is 30% or more. A method for producing a polypropylene-based resin foam sheet having a content of at least 10% has been proposed.

[0004]

However, this method is
When a polypropylene-based resin foam sheet and a cloth-based or resin-based skin material are laminated and used, since the skin material generally has a weight more than twice that of the polypropylene-based foam sheet, even if the polypropylene-based foam sheet has a longitudinal direction. Has a thermal shrinkage of 10% or more, and has a thermal expansion coefficient of 30 in the thickness direction.
If the heat shrinkage force is weak, the drawdown or the abnormal waving phenomenon cannot be eliminated even if the heat shrinkage is too high. This is because the insufficient heat shrinkage of the polypropylene foam sheet occurs when the resin strength and the degree of crosslinking are small.

The present invention solves the above-mentioned conventional problems, and as a material for obtaining a vacuum-formed product excellent in appearance without wrinkles or irregularities, without causing drawdown or abnormal waviness during vacuum forming. The object is to provide a polypropylene-based resin foam and a polypropylene-based resin foam laminate that can be provided.

[0006]

The first aspect of the present invention is 50% by weight.
A polypropylene resin foam comprising the above polyolefin resin composition containing a polypropylene resin, comprising:
The heat shrinkage force S ₁ per unit length in the longitudinal direction and the width direction of the foam at 30 ° C. to 200 ° C. is S ₁ ≧ 4 × with respect to the weight W ₁ per unit length of the foam having the same width. It is a polypropylene-based resin foam having a relationship of W ₁ .

In the present invention 1, as the polyolefin resin in the polyolefin resin composition, in addition to polypropylene resin, a block copolymer or a random copolymer of propylene and an olefin monomer such as ethylene or α-olefin. Examples include terpolymers of propylene, ethylene, butene, and the like. These polymers may be used alone or in combination of two or more.

It is necessary that the olefin resin contains 50% by weight or more of polypropylene resin. When the content of the polypropylene resin is less than 50% by weight, it becomes difficult to maintain the heat shrinkage force specified in the present invention 1,
Further, it becomes difficult to satisfy the heat resistance and vacuum formability required for the interior material.

In the present invention 1, the polyolefin resin composition contains a thermal decomposition type foaming agent for the polyolefin resin. As the thermal decomposition type foaming agent, it is possible to use anything as long as it has a decomposition temperature higher than the melting temperature of the polyolefin resin composition, for example,
Azodicarbonamide is preferably used, and further, hydrazodicarbonamide, azodicarboxylic acid amide, azodicarboxylic acid barium salt, dinitrosoguanine, p, p ′ having a decomposition temperature equal to or higher than that of azodicarbonamide. ─ oxybisbenzenesulfonyl semicarbazide, trihydrazine symmetric triazine,
Examples thereof include bisbenzenesulfonyl hydrazide, barium azodicarboxylate, azobisisobutyronitrile and toluenesulfonyl hydrazide. These thermal decomposition type foaming agents may be used alone or in combination of two or more.

The amount of the thermal decomposition type foaming agent added is 2 to 25% by weight in the polyolefin resin. When the addition amount is less than 2% by weight, only a low expansion ratio can be obtained. On the contrary, when the addition amount is more than 25% by weight, the expansion ratio is too high and the strength, heat resistance and vacuum formability are high. Spoil.

In the present invention 1, the polyolefin resin composition contains a crosslinking accelerator for the polyolefin resin. Examples of the crosslinking accelerator include civinylbenzene, diallylbenzene, divinylnaphthalene, polyethylene dimethacrylate, trimethylolpropane trimethacrylate, triallyl isocyanurate and the like.

The addition amount of the crosslinking accelerator is preferably 0.01 to 30% by weight, more preferably 0.05 to 15% by weight in the polyolefin resin. Addition amount is 0.
If it is less than 05% by weight, a sufficient degree of crosslinking cannot be obtained,
It becomes difficult to produce a clean foam that maintains closed cells. Conversely, if it exceeds 30% by weight, the degree of crosslinking becomes excessive, and it becomes difficult to produce a clean foam that maintains closed cells. Not only that, the elongation at high temperature becomes small and the vacuum formability is impaired.

Further, this crosslinking accelerator and an organic peroxide can be used in combination. As the organic peroxide, for example,
Examples thereof include methyl ethyl ketone peroxide, t-butyl peroxide, dicumyl peroxide and the like. When an organic peroxide is used in combination, it is preferably contained in the polyolefin resin in advance in an amount of preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight. The chemical crosslinking and the ionizing radiation crosslinking may be used in combination.

In the present invention 1, the degree of crosslinking of the polyolefin resin is preferably 10 to 70%. When the degree of cross-linking is less than 10%, the vacuum formability is improved, but the heat resistance and compression set resistance when used as an interior material is inferior, and it easily becomes tired for a long time, and conversely exceeds 70%. In this case, the elongation at high temperature tends to be poor and sufficient vacuum formability cannot be obtained.

In the present invention 1, the polypropylene resin foam has a thermal contraction force S ₁ per unit length in the longitudinal and width directions of the foam at 130 ° C. to 200 ° C. It is necessary to have the relationship of S ₁ ≧ 4 × W ₁ ... Formula (1) with respect to the weight W ₁ per length. In the case of S ₁ <4 × W ₁ , an abnormal waving phenomenon occurs in the polypropylene resin foam during vacuum forming, and only a vacuum formed product having wrinkles and irregularities and having a poor appearance can be obtained.

A method for producing a polypropylene resin foam in the present invention 1 is, for example, polypropylene containing the above-mentioned polypropylene resin, a thermal decomposition type foaming agent, a crosslinking accelerator and other additives as appropriate. Using the resin composition, a non-foamed sheet is prepared by melt molding at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent and the crosslinking accelerator,
This unfoamed sheet was heated to a temperature below the decomposition temperature of the heat-decomposable foaming agent and above the decomposition temperature of the crosslinking accelerator, or was irradiated with ionizing radiation to crosslink to the above-mentioned degree of crosslinking and crosslinked. A method in which an unfoamed sheet is heated to a temperature equal to or higher than the decomposition temperature of the thermal decomposition type foaming agent to obtain a foamed sheet, and the foamed sheet is cooled to obtain a foam can be adopted.

At this time, in order to develop the heat shrinkage force, for example,
For example, the following method can be adopted. Unfoamed sheet
Foamed sheet obtained by foaming under pressure
Cool under tension. As the tension at this time
Is 0.07 to 2.0 kg / cm ²Is preferred.
The foamed sheet is stretched in the transverse direction and then cooled. This stretch
Has a tension of 0.04 to 1.5 kg / cm²A range of
Good In vertical foaming, the width of the foamed sheet immediately after foaming
Quench to avoid shrinkage.

The second aspect of the present invention is 50% by weight or more of polypropylene.
Of a polyolefin resin composition containing a ren resin
Polypropylene laminated with skin material on propylene resin foam
A pyrene-based resin foam laminate, which is from 130 ° C to 20
Heat absorption per unit length in the longitudinal and width directions at 0 ℃
Contraction S₂Is the weight W per unit length of foam of the same width ₂
And the weight W per unit length of skin material of the same width₃Against
S₂≧ 0.7 × (W ₂+ W₃) Poly relationship
It is a propylene resin foam laminate.

In Invention 2, the same polyolefin resin composition as in Invention 1 is used.

In the second aspect of the present invention, as the skin material, if it is a cloth type, polyester type, polyamide type, acrylic resin type synthetic fiber or natural fiber such as cellulose, or if it is a resin type, polyvinyl chloride type, Any material such as a thermoplastic elastomer system may be used.

As a method for laminating the polypropylene resin foam and the skin material, a method of adhering with an adhesive, a method of heat laminating, a method of extrusion laminating and the like can be arbitrarily adopted.

In the present invention 2, the heat shrinkage force S ₂ per unit length in the longitudinal direction and the width direction at 130 ° C. to 200 ° C. of the laminated product of the foam and the skin material is the same as that of the foam having the same width. For weight W ₂ per unit length in the width and width directions and weight W ₃ per unit length for skin material of the same width, S ₂ ≧ 0.7 × (W ₂ + W ₃ ) It is necessary to have the relationship of (2).

When S ₂ <0.7 × (W ₂ + W ₃ ), an abnormal waviness phenomenon occurs in the polypropylene resin foam during vacuum forming, and only a vacuum-formed product having wrinkles or irregularities and a poor appearance is obtained. I can't.

In the present invention 2, as a method for producing a polypropylene resin foam laminated product, for example, the present invention 1
A method is used in which a foam is obtained by the same method as above and a skin material is laminated on the foam. Further, as a method for expressing the heat shrinkage force, the same method as in the first aspect of the invention is adopted.

[0025]

[Function] The polypropylene resin foam of the present invention 1 has 5
A polypropylene resin foam comprising a polyolefin resin composition containing 0% by weight or more of a polypropylene resin, wherein the heat shrinkage force S ₁ per unit length in the longitudinal and width directions of the foam at 130 ° C. to 200 ° C. For a weight W ₁ of a foam having the same width per unit length, S ≧ 4 ×
By having the relationship of W ₁ , it is possible to use it as a material for obtaining a vacuum-formed product excellent in appearance without wrinkles or irregularities without causing drawdown or abnormal waviness during vacuum forming.

The polypropylene resin foam laminate of the present invention 2 is a polypropylene resin foam laminate in which a skin material is laminated on a polypropylene resin foam comprising a polyolefin resin composition containing 50% by weight or more of polypropylene resin. A heat-shrinking force S ₂ per unit length in the longitudinal direction and width direction at 130 ° C. to 200 ° C. is a skin material having the same weight W ₂ per unit length and the same width. S ₂ ≧ 0.7 for the weight W ₃ per unit length of
By having the relationship of × (W ₂ + W ₃ ), it can be used as a material for obtaining a vacuum-formed product excellent in appearance without wrinkles or irregularities without causing drawdown or abnormal waviness during vacuum forming. .

[0027]

EXAMPLES The present invention will be described below with reference to examples. Example 1 A polypropylene resin composition comprising 70 parts by weight of polypropylene-ethylene random copolymer, 30 parts by weight of linear polyethylene, 12 parts by weight of azodicarboxylic acid amide, and 2 parts by weight of divinylbenzene was extruded with an extruder. An unfoamed sheet was obtained.

The unfoamed sheet is crosslinked by irradiating with ionizing radiation to obtain an unfoamed sheet (degree of crosslinking 40%).
%) Was obtained. This cross-linked unfoamed sheet is heated to 220 ° C. in a foaming machine and the longitudinal tension is 0.1 kg / cm.
Foam at ² , and simultaneously tension in the width direction is 0.05 kg / cm
After stretching in the width direction at ² , cool to a foaming ratio of 25
A polypropylene foam having a thickness of 3 mm was obtained.

The heat shrinkage force S ₁ in the longitudinal direction and the width direction of the obtained polypropylene-based foam was measured as follows. The results are shown in Table 1. Measurement part length of measurement sample 4
The weight W ₁ of cm and width 2.5 cm (area 10 cm ² ) was measured and found to be 0.12 g. This polypropylene-based foam satisfies the relationship of formula (1) in both the longitudinal direction and the width direction.

Method of measuring shrinkage force The foam was cut into a length of 9 cm and a width of 2.5 cm to obtain a measurement sample, and the measurement sample was heated in advance to 160 ° C. in a heating oven attached to the tensile tester. , The distance between chucks of the tensile tester is set to 4 cm. After attaching the measurement sample to the chuck, the heating oven is closed. Since the measurement sample thermally expands and sags, the chuck is moved to eliminate this slack. Then, it is left for 5 minutes and the maximum value of the heat shrinkage force appearing on the load detector is read, and this is designated as S ₁ (g).

Further, a skin material [polyvinyl chloride sheet: length 4 cm, width 2.5 cm] is added to the polypropylene foam.
A stacking test of a (area of 10 cm ² ) weight of 0.40 g] was performed by a vacuum molding machine. The results are also shown in Table 1. The molding test by the vacuum molding machine was conducted as follows. The sample for measurement is preheated with an infrared heater so that the surface temperature is 160 ° C, and vacuum-molded with a cup-shaped mold designed to have a drawing ratio of 0.6. The appearance of wrinkle appearance was observed.

COMPARATIVE EXAMPLE 1 A polypropylene resin composition comprising 55 parts by weight of polypropylene-tyrene copolymer, 45 parts by weight of linear polyethylene, 12 parts by weight of azodicarboxylic acid amide, and 2.0 parts by weight of divinylbenzene was used in an extruder. To obtain an unfoamed sheet.

This unfoamed sheet is crosslinked by irradiating with ionizing radiation (crosslinking degree 32.
%) Was obtained. This cross-linked unfoamed sheet is heated to 220 ° C. in a foaming machine to give a longitudinal tension of 0.05 kg / c.
It was foamed at m ² , stretched at a tension in the width direction of 0.02 kg / cm ² and then cooled to obtain a polypropylene foam having a foaming ratio of 25 times and a thickness of 3 mm.

The heat shrinkage force (S ₁ ) in the longitudinal direction and the width direction of the obtained polypropylene-based foam was measured. The results are shown in Table 1. 1. Length of measurement portion of measurement sample is 4 cm, width 2.
The weight W ₁ of 5 cm (area 10 cm ² ) was measured and found to be 0.12 g. This polypropylene foam is
The relationship of Formula (1) was not satisfied in the width direction.

A molding test was carried out by a vacuum molding machine for a laminate of the polypropylene foam and the same skin material as in Example 1. The results are also shown in Table 1.

[0036]

[Table 1]

As is clear from Table 1, in the case of Example 1 of the present invention, a vacuum-formed product having excellent vacuum formability, no abnormal waviness during vacuum forming, and no wrinkles or unevenness was obtained. I was able to. On the other hand, in Comparative Example 1, abnormal waviness was generated during vacuum forming, and only a vacuum formed product having wrinkles and unevenness and a poor appearance could be obtained.

Examples 2 to 5 In the same manner as in Example 1, except that the polypropylene foams obtained in Example 1 and the skin materials shown in Table 1 were laminated, the measurements were carried out in the longitudinal direction. Also, the heat shrinkage force S ₂ (g) in the width direction was measured. The results are shown in Table 2. Measurement part length of measurement sample 4cm, width 2.5c
The weight W ₁ of m (area 10 cm ² ) was measured and found to be 0.
It was 12 g. For each of them, the relation of the formula (2) was satisfied in both the longitudinal direction and the width direction.

A molding test was carried out by a vacuum molding machine on the polypropylene foam laminated with the skin material shown in Table 2. The results are also shown in Table 2.

Comparative Examples 2 to 4 In the same manner as in Example 1 except that the polypropylene foams obtained in Comparative Example 1 and the skin materials shown in Table 2 were laminated, the measurement was performed in the same manner as in Example 1 in the longitudinal direction. Also, the heat shrinkage force S ₂ (g) in the width direction was measured. The results are also shown in Table 2. The weight W ₁ of the measurement portion of the measurement sample having a length of 4 cm and a width of 2.5 cm (area: 10 cm ² ) was measured and found to be 0.12 g. For each of them, the relation of Expression (2) was not satisfied in the width direction.

A molding test was carried out by a vacuum molding machine in the same manner as in Example 1 on the polypropylene foam laminated with the skin material shown in Table 2. The results are also shown in Table 2.

[0042]

[Table 2]

As is clear from Table 2, in the cases of Examples 2 to 5 of the present invention, all of them have excellent vacuum formability, no abnormal waviness occurs during vacuum forming, and no wrinkles or irregularities. A vacuum molded product could be obtained. On the contrary,
In each of Comparative Examples 2 to 4, abnormal waviness was generated during vacuum forming, and only a vacuum formed product having wrinkles and unevenness and a poor external appearance could be obtained.

[0044]

EFFECTS OF THE INVENTION Since the polypropylene resin foam and the polypropylene resin foam laminate of the present inventions 1 and 2 have the above-mentioned constitutions respectively, they cause drawdown and abnormal waviness during vacuum forming. Without
It can be used as a material for obtaining a vacuum-formed product having an excellent appearance without wrinkles or irregularities.

Claims (2)

[Claims] 1. A polypropylene-based resin foam comprising a polyolefin-based resin composition containing 50% by weight or more of a polypropylene resin, the polypropylene-based resin foam having a unit length in a longitudinal direction and a width direction at 130 ° C. to 200 ° C. The polypropylene resin foam, wherein the heat shrinkage force S ₁ has a relationship of S ₁ ≧ 4 × W ₁ with respect to the weight W ₁ per unit length of the foam having the same width. 2. A polypropylene-based resin foam laminate obtained by laminating a skin material on a polypropylene-based resin foam made of a polyolefin-based resin composition containing 50% by weight or more of a polypropylene resin at 130 to 200 ° C. Heat shrinkage force S ₂ per unit length in the longitudinal and width directions
Is S ₂ ≧ for the weight W ₂ of the foam having the same width per unit length and the weight W ₃ of the skin material having the same width per unit length.
A polypropylene resin foam laminate having a relationship of 0.7 × (W ₂ + W ₃ ).