JPH085984B2 - Polypropylene resin composition for foam, laminated sheet and laminated body - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin composition for foams, a laminated sheet and a laminated body using the composition. Specifically, the present invention relates to a polypropylene-based resin composition for a foam capable of easily and efficiently obtaining a foamed resin body having a high expansion ratio, an automobile interior part obtained by using the composition, specifically The present invention relates to a polypropylene laminated sheet and a laminated body, which are suitable for being attached to an inner wall portion, a seat, a backrest, etc. of an automobile and are lightweight and have excellent bending rigidity.

[0002]

2. Description of the Related Art As a method for producing a foam based on a polyolefin resin, there is a method in which a chemical foaming agent is added to the polyolefin resin and then the resin is heated and melted to foam. For example, in the case of obtaining a polypropylene-based resin foam, azodicarbonamide, which is a foaming agent generally used, is added to the polypropylene-based resin, and then the resin composition is heated and melted.

On the other hand, sheet-like parts used as interior materials for automobiles are required to have excellent appearance, light weight, high bending rigidity, and low production cost.

[0004] Conventionally, in order to obtain a good appearance in an automobile interior sheet, a woven or non-woven fabric satisfying the demand has been attached to a sheet-like base material as a base. For example, a sheet made of a thermoplastic resin such as a polyolefin-based resin is used as the sheet-shaped substrate, and a sheet-shaped material such as a woven fabric or a nonwoven fabric is laminated as a skin material on the sheet-shaped substrate to obtain a sheet-shaped substrate. The laminated body is formed into a desired shape by thermoforming.

[0005]

In the method for producing a polyolefin resin foam using the above-mentioned chemical foaming agent, the foaming ratio of the resulting foam is slightly different depending on the kind and the amount of the foaming agent used, but at most twice. It is difficult to easily obtain a desired foam having a high expansion ratio of 2 times or more.

Further, in the conventional sheet-like laminated body, if the thickness of the resin sheet as the base material is reduced in order to reduce its weight, the bending strength of the base material is lowered. Therefore, in order to solve this problem, if a filler is mixed into the resin sheet material to increase the rigidity of the base material itself, the specific gravity increases, so that it becomes necessary to make the thickness even thinner. It has been extremely difficult to achieve the improvement in rigidity together.

The present invention solves the above-mentioned problems of the prior art and makes it possible to easily and efficiently obtain a foam having a high expansion ratio, and a polypropylene resin composition for foam, and a lightweight resin composition obtained by using the same. Moreover, it is an object of the present invention to provide a laminated sheet and a laminate having excellent bending rigidity.

[0008]

A polypropylene-based resin composition for foam according to claim 1 is a polypropylene-based resin 10
0.5 to 10 parts by weight of a porous filler, which is previously impregnated with 0% by weight of water in an amount of 2% by weight or more, and a chemical foaming agent of 0.1 to 1
It is characterized by being mixed with parts by weight.

The laminated sheet of claim 2 is a laminated sheet in which an upper layer and a lower layer are laminated with an intermediate layer interposed therebetween, wherein the upper layer and the lower layer are solid resin layers made of polypropylene resin, and the intermediate layer. Is a foamed resin layer obtained by foaming the polypropylene resin composition according to claim 1 at a foaming ratio of 2 times or more.

According to a third aspect of the present invention, a laminated sheet according to the second aspect is formed by laminating a stretchable skin material on one surface.

That is, in view of the above conventional problems, the present inventors have earnestly studied a method for easily and efficiently obtaining a foam having a high expansion ratio by adding and melting a composition comprising a polypropylene resin and a chemical foaming agent. As a result, by adding a porous filler impregnated with a specific amount of water in advance to a composition consisting of a polypropylene resin and a chemical foaming agent, foaming is achieved by the synergistic effect of the porous filler and the compounding foaming agent. It was found that a highly expandable resin foam having improved foamability and a foaming ratio of 2 or more can be obtained.

In addition, the inventors of the present invention have made extensive studies as to the weight reduction of the resin sheet and the improvement of the bending rigidity of the base material. As a result, the outer layer and the inner layer are solid layers made of polypropylene resin, and the intermediate layer is polypropylene type. It has been found that the above object can be achieved by using a three-layer laminated sheet made of a resin and having a foaming ratio of 2 times or more. The present invention has been completed based on the above findings.
The present invention will be described in detail below.

In the polypropylene resin composition for foams according to claim 1, as the polypropylene resin used as a raw material, for example, crystalline isotactic propylene homopolymer or ethylene having a low ethylene unit content is used. A copolymer part composed of a propylene random copolymer or a homopolymer part composed of a propylene homopolymer and a copolymer part composed of an ethylene propylene random copolymer having a relatively large content of ethylene units,
A substantially crystalline block copolymer of propylene and ethylene, which is commercially available as a so-called propylene block copolymer, or each homopolymerization part or copolymerization part in this block copolymer further includes butene-1 and the like. Substantially crystalline propylene obtained by copolymerizing α-olefin
Examples thereof include ethylene-α-olefin copolymers.

If desired, various additives such as a heat stabilizer, a UV absorber, an antioxidant and a colorant may be added to the polypropylene resin. As a polypropylene resin, the melt index (MF
Those in which R) is in the range of 0.5 to 20 g / 10 minutes are preferably used.

As the chemical foaming agent, decomposition type foaming agents which generate gas by heating, for example, azodicarbonamide, dinitropentamethylenetetramine, azodiisobutyronitrile and the like can be mentioned. The compounding amount of the chemical foaming agent is 0.1 to 1 part by weight, preferably 0.2 to 0.8 part by weight, based on 100 parts by weight of the polypropylene resin. If the compounding amount of this chemical foaming agent is less than 0.1 parts by weight, the foaming effect is not sufficient, and if it is more than 1 part by weight, the cells (bubbles) formed by foaming become too large and the bubbles burst. On the contrary, the expansion ratio decreases, etc.
Foam moldability deteriorates.

The porous filler is not particularly limited as long as it is a porous inorganic substance, and for example, diatomaceous earth, activated carbon, calcium carbonate, calcium chloride, molecular sieve and the like are used. The amount of water impregnated into such a porous filler is 2% by weight or more, preferably 2 to 20% by weight, and more preferably 5 to 1% with respect to the porous filler.
It is in the range of 5% by weight. When the impregnated amount of the water is less than 2% by weight, the synergistic effect due to the combined use with the chemical foaming agent cannot be sufficiently obtained. Further, if the amount of impregnation is too large, the foaming phenomenon at the time of molding remarkably increases and the moldability deteriorates. Therefore, the amount of impregnation of the water is preferably 20% by weight or less.

The amount of the porous filler impregnated with the above-mentioned water in a specified amount is 0.5 to 10 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the polypropylene resin. If the compounding amount of the porous filler is less than 0.5 part by weight, the foaming property at the time of molding becomes insufficient.
If it is more than weight part, the mechanical strength of polypropylene resin,
In particular, properties such as impact strength decrease.

The polypropylene resin composition of the present invention comprises
It can be appropriately heat-melted and foam-molded by a conventional method. As the foaming method, for example, an extruding machine or an injection molding machine is used to heat and melt under pressure, extrude under normal pressure, or extrude into a forming mold, or inject into a molding die to foam. There is a way. In addition, after heating and melting under pressure in an airtight container, foaming may be performed by removing the pressurized state, or pressure-melting and foaming may be performed under normal pressure.

In foam molding, a small amount of talc, inorganic powder such as silica, metal oxides such as zinc white (zinc oxide) and litharge (lead oxide) are used as a foam control agent for the foaming agent.
Fatty acids such as stearic acid and lauric acid or metal salts of these fatty acids (for example, salts of zinc, calcium, lead, barium, etc.) may be added.

Next, the present invention having a foamed resin layer consisting of substantially closed cells, which is formed by foaming such a polypropylene resin composition for foams of the present invention at a foaming ratio of 2 times or more, as an intermediate layer. The manufacturing method of the laminated sheet of is described.

In the laminated sheet of the present invention, the polypropylene resin used in the above-mentioned polypropylene resin composition can be used as the polypropylene resin constituting the upper and lower solid resin layers.

Here, the polypropylene resin constituting the upper layer and the polypropylene resin constituting the lower layer may be the same or different, and the upper layer and / or
Alternatively, the polypropylene resin forming the lower layer and the polypropylene resin used for the intermediate layer may be the same or different.

The laminated sheet of the present invention can be produced by a lamination method such as a heat bonding method, an extrusion or dry lamination method, and a coextrusion method, and the coextrusion method is particularly preferable.

In the case of the coextrusion method, either inflation molding or T-die molding can be adopted. For example, when T die molding is adopted, a multi-manifold T die or a multi-layer die such as a device having a feed block between the extruder and the T die (T die with a feed block) is used to obtain 160 to 200. The laminated sheet of the present invention can be produced by a coextrusion method such as a two-kind three-layer or a three-kind three-layer at a molding temperature of ° C. That is, the constituent resin of each layer is melted by heating in an extruder and extruded from a T-die. In this extruder, the foamed resin layer of the intermediate layer is melt-kneaded with the resin and the foaming agent under pressure, and immediately after the die exit, is extruded and foamed under a low pressure atmosphere. It is coextruded to obtain a laminated sheet.

In the laminated sheet of the present invention, the foaming ratio of the foamed resin layer as the intermediate layer is 2 times or more, preferably 2 to 5
It is twice, more preferably 2 to 4 times. The foaming ratio of the foamed resin layer can be easily adjusted to a desired ratio by appropriately combining the type of the chemical foaming agent of the polypropylene resin composition and its addition amount, the addition amount of the porous filler and its water content, molding temperature, etc. can do.

The laminated sheet of the present invention has a thickness of 5
The thickness of the upper and lower layers sandwiching the intermediate layer is preferably 0.05 to 2 mm, and the thickness of the intermediate layer is preferably 1 to 4.9 mm. That is, according to the laminated sheet of the present invention, the thickness of 5
If the thickness is 5 mm or less, sufficient strength is obtained as an interior material for automobiles, and if the thickness exceeds 5 mm, the cost increases, which is not preferable.

It should be noted that the laminated sheet of the present invention has a higher flexural rigidity than that of a sheet having the same weight per unit area and the same composition and having only a solid layer containing no foamed portion. For example, 1.1 times or more,
It is desirable to have a physical property in the range of preferably 2 to 5 times, more preferably 2 to 4 times. In order to obtain a laminated sheet having these physical properties, the foaming conditions of the intermediate layer, for example, the adjustment of the expansion ratio by the type of the chemical foaming agent and its addition amount, the molding temperature, or an appropriate combination of the thickness of the intermediate layer, It suffices to balance the reduction in weight and the improvement in bending rigidity.

The laminated sheet of the present invention is basically a three-layer laminated sheet consisting of an upper layer, an intermediate layer and a lower layer,
An adhesive layer, a second intermediate layer, or the like may be interposed if necessary.

The laminated body of the present invention is obtained by laminating a stretchable skin material on one surface of the laminated sheet of the present invention.

The skin material used in the laminate of the present invention comprises one or more thermoplastic resin fibers such as polyethylene fibers, polypropylene fibers, polyester fibers, polyamide fibers, polystyrene fibers and polyacrylic fibers. Non-woven fabric, woven fabric, artificial leather, or a stretchable sheet or mat-like material such as a soft plastic film or sheet is used. Here, having elasticity means that when it is pulled by a force of 50 kg / cm ² , the elongation rate is 5% or more.

In order to laminate and integrate such a skin material, an ethylene-vinyl acetate copolymer, ethylene-propylene rubber, unsaturated carboxylic acid-modified polyolefin may be provided on one surface of the laminated sheet of the present invention, if necessary. A skin material is laminated via an adhesive resin such as a resin and bonded by heat bonding or extrusion laminating.

At this time, the laminated sheet has a melting point of the material resin constituting the laminated sheet of ± 30 ° C., particularly a melting point of ± 20.
It is preferable to laminate with the skin material while maintaining the temperature within the range of ° C. If the bonding temperature at the time of lamination is higher than the above temperature, the air bubbles in the intermediate layer of the laminated sheet are destroyed, and the strength of the laminated body is reduced. Also, when adhering the skin material, 1.5 to 5
Roll pressure bonding is preferably performed at a pressure within the range of kg / cm ² .

The laminate obtained as described above is thermoformed into a desired shape when it is used as an automobile interior material, for example. Thermoforming is usually performed with the melting point of the resin constituting the laminate ±
It is carried out at a temperature in the range of 30 ° C., preferably in the range of the melting point of the constituent resin ± 20 ° C.

As a heating method in this thermoforming, any method can be adopted, for example, hot air heating method,
A radiant heat heating method using an infrared heater, a far infrared heater or the like can be used. As the thermoforming method, a vacuum forming method, a pressure forming method, a vacuum pressure forming method, a stamping forming method, or the like, which is widely used in general, is used.

The production of a laminated sheet, a laminated body by laminating a laminated sheet and a skin material, and a molded article from the laminated body in the present invention are extremely efficient by carrying out the following steps continuously. In addition, the cost can be reduced.

The laminated sheet as the base material is extruded (T
The resin composition as an intermediate layer is extruded from a die, and is foamed immediately after the exit of the die, and the solid layers on both outer sides are co-extruded with the resin composition sandwiched therebetween.

While maintaining the laminated sheet obtained by coextrusion as described above at a temperature within the range of the melting point of the material resin ± 30 ° C., the skin material is laminated by roll pressure bonding, or both are bonded by an adhesive. Roll crimp through.

The laminated body obtained above is maintained at a temperature within the range of the melting point of the constituent resin ± 30 ° C., and immediately put into a thermoforming machine without lowering the temperature to perform thermoforming.

[0039]

In the present invention, the reason why the expansion ratio can be increased by adding a porous filler impregnated with a specific amount of water to a mixture of a polypropylene resin and a chemical foaming agent is not clear. It is presumed that the synergistic effect of the foaming agent and the porous filler impregnated with water significantly improves the foamability and increases the expansion ratio of the resulting foam. By the way, according to the polypropylene-based resin composition for foams of the present invention, it is possible to highly expand the foaming ratio of 1.3 to 1.5 times from the conventional one to 2 to 5 times.

Therefore, according to the laminated sheet of the present invention having as the intermediate layer a foamed resin layer formed by foam-molding such a highly expandable polypropylene resin composition with an expansion ratio of 2 or more, the intermediate layer The highly foamed resin layer achieves weight reduction and a great improvement in bending rigidity.

Further, according to the laminated body obtained by laminating the skin material on the laminated sheet, a laminated material suitable as an interior material for various automobiles is provided.

[0042]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Example 1 Impact polypropylene (propylene-ethylene block copolymer) (MFR: 1.18 / 10 at 230 ° C.)
Min) 100 parts by weight, 0.3 parts by weight of a chemical foaming agent (azodicarbonamide) and 5 parts by weight of diatomaceous earth impregnated with 9% by weight of water are uniformly mixed with a Henschel mixer, and a 711 mm wide T A single screw extruder (screw diameter: 65 mmφ) equipped with a die was used to perform extrusion molding into a sheet at a molding temperature of 200 ° C. The expansion ratio of the obtained sheet is 3.
It was 0 times.

Example 2 A sheet was extruded in the same manner as in Example 1 except that the diatomaceous earth impregnated with 6% by weight of water was used. The expansion ratio of the obtained sheet is 2.
It was 0 times.

Comparative Example 1 Extrusion molding was carried out in the form of a sheet by the same method as in Example 1 except that diatomaceous earth was not added at all. The expansion ratio of the obtained sheet was 1.5 times.

Example 3 Using a T-die coextrusion multi-layer sheet manufacturing apparatus with a feed block, a three-layer laminated sheet having a foam resin layer as an intermediate layer and solid resin layers laminated on both outer surfaces was produced. From the first extruder (50 mmφ) of the apparatus, impact-resistant polypropylene (propylene-ethylene block copolymer) which becomes the respective upper and lower solid resin layers of the three-layer laminated sheet
(MFR, 1.1 g / 10 minutes at 230 ° C.) was extruded, and from the second extruder (63.5 mmφ), 100 weight of the same impact-resistant polypropylene as the material of the solid resin layer, which becomes the foamed resin layer of the intermediate layer 0.6 parts by weight of a chemical foaming agent (azodicarbonamide) and 2.5 parts by weight of diatomaceous earth preliminarily impregnated with water of 9% by weight were extruded.

The molding temperature was 170 ° C., the mixture was coextruded, and the melted resin was joined into three layers, and then extruded into a sheet, which was then covered with a surface material (polyester fiber non-woven fabric, thickness: 150 g / m 2 by weight per unit area). ² ) was laminated by roll pressure bonding to form a laminate, which was subsequently molded by vacuum pressure forming to obtain a molded product with a high-class appearance.

The resin types of the upper and lower solid resin layers and the foamed resin layer of the intermediate layer in the laminated sheet manufactured in this example (the above impact polypropylene, hereinafter referred to as "P").
It is abbreviated as "P". ), Thickness, weight, thickness and weight of a laminated sheet obtained by laminating these, flexural rigidity measured by the following method (1), and weight reduction ratio measured by the following method (2).
Shown in The bending rigidity of the obtained laminated sheet was about 3 times that of the solid resin sheet having the same weight per unit area and the same composition and having no foamed portion.

(1) Bending rigidity Test piece: 50 mm (width) × 150 mm (length) Method: According to JIS K7203. Condition: Distance between fulcrums = 100 mm Pressing speed = 50 mm / min The force (g) required to bend the test piece by 10 mm is determined and used as the bending rigidity value.

(2) Weight reduction ratio Conventionally, a base material of a laminated sheet for automobile interior parts of the type used (of Comparative Example 1 described later, a solid resin sheet having a thickness of 1.8 mm, per unit area) Weight 1620g /
m ² ) as a standard product, and is calculated from the difference in weight with the sample to be measured as shown in the following formula. Weight reduction rate (%) = {1620 (g / m ² ) −Sample weight (g / m ² )} / 1620 (g / m ² ) × 100 Example 4, Comparative Example 2 and Comparative Example 3 Lamination of the present invention In the sheet, in order to clarify that the use of the foamed resin layer as the intermediate layer improves the bending rigidity and reduces the weight as compared with the base sheet having no such foamed resin layer, Example 4, Comparative Example 2 and Comparative Example 3 is shown.

As shown in Table 1, the laminated sheet obtained in Example 4 was different only in the thickness of the intermediate layer and the weight per unit area, and the other constitutions were the same as those of the laminated sheet obtained in Example 3. The extrusion molding was performed in the same manner.

Further, as shown in Table 1, Comparative Examples 2 and 3 do not have an intermediate layer and are composed only of a solid resin layer of PP. In Comparative Examples 2 and 3, extrusion molding was performed at a molding temperature of 230 ° C.

The flexural rigidity of each sheet was examined,
The weight reduction rate of the laminated sheet of Example 4 was examined, and the results are shown in Table 1.

[0054]

[Table 1]

In Table 1, the following is clear from the comparison between Example 4 and Comparative Example 2. That is, when the same flexural rigidity of the base material sheet is to be obtained as 1500 g, a resin amount of 900 g / m ² is sufficient for the laminated sheet of the present invention,
Comparative Example 2 requires a resin amount of 1620 g / m ² .

From the comparison between Example 4 and Comparative Example 3,
The following is clear. That is, based on the weight of the solid resin base material sheet of Comparative Example 2 of 1620 g / m ² , Example 4 shows a weight reduction rate of 44%. Attempting to achieve the same weight reduction of 44% with a solid resin base sheet,
The laminated sheet of Example 4 exhibits a bending rigidity of 1500 g, whereas the sheet of Comparative Example 3 can obtain a bending rigidity of only 250 g. That is, Example 4 and Comparative Example 3 have the same weight per unit area and the same composition, but the flexural rigidity of the former is 6 times that of the latter.

[0057]

As described in detail above, according to the polypropylene resin composition for foams of the present invention, a highly expandable resin composition which can be easily and efficiently foam-molded with a high expansion ratio of 2 times or more. Provided.

Therefore, according to the laminated sheet and the laminated body of the present invention having the foamed resin layer made of the polypropylene resin composition for a foamed body of the present invention as an intermediate layer,
A material which is lightweight and excellent in bending rigidity and which is suitable as an interior material for automobiles is provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Adachi 3-10 Shiodori, Kurashiki-shi, Okayama Prefecture Mizushima Plant, Mitsubishi Kasei Co., Ltd. (72) Inventor Tomohio Ohata 3-12-20 Kamisooka, Shiki City, Saitama Prefecture Kumi Kasei Co., Ltd. (72) Inventor Hide Nakai, 3-12-20 Kamisooka, Shiki City, Saitama Prefecture Kumi Kasei Co., Ltd.

Claims (3)

[Claims] 1. To 100 parts by weight of polypropylene resin,
Porous filler impregnated with water in an amount of 2% by weight or more in advance.
A polypropylene resin composition for a foam, which comprises 5 to 10 parts by weight and 0.1 to 1 part by weight of a chemical foaming agent. 2. A laminated sheet in which an upper layer and a lower layer are laminated with an intermediate layer interposed therebetween, wherein the upper layer and the lower layer are solid resin layers made of polypropylene resin, and the intermediate layer is the same as in claim 1. A laminated sheet, which is a foamed resin layer obtained by foaming the polypropylene-based resin composition as described above at a foaming ratio of 2 or more. 3. On one surface of the laminated sheet according to claim 2,
A laminate formed by laminating elastic skin materials.