JPS5898341A - Foamable composite resin sheet - Google Patents

Abstract

PURPOSE:To provide the titled sheet suitable for a core material in the production of an interior automotive trim, by extruding in sheet form under nonfoamed conditions a foamable polyolefin resin composition with a filler. CONSTITUTION:100pts.wt. resin base comprising a blend of polypropylene and polyethylene (or propylene/ethylene copolymer), 42-100pts.wt. cellulosic filler (e.g., woodmeal), 0.5-3pts.wt. radical generator (e.g., cumene hydroperoxide), 4-15pts.wt. foaming agent (e.g., hydrazocarbonamide), and 2.5-15pts.wt. crosslinker (e.g., divinylbenzene) are mixed together. The resulting mixt. is extruded at about 170-190 deg.C to form a non-crosslinked, nonfoamed foamable composite resin sheet. A composite resin molding with a light-wt., foamed core may be formed by putting the above sheet in between skin materials and causing the sheet to foam while thermoforming.

Description

[Detailed description of the invention] The present invention applies during press molding and vacuum forming.

This invention relates to a foamable composite resin sheet that induces a crosslinking reaction and is foamable.

For example, core materials used in automobile interior materials include polypropylene resin alone, ABS resin, or composite resins made by mixing polypropylene resin with cellulose fillers such as wood flour, talc, calcium carbonate, etc. as fillers. There is.

However, such a core material generally has a high specific gravity of 1.0 or more and is heavy.
Also, in the case of composite resins such as those mentioned above.

Although the material cost is low because a large amount of cellulose filler such as wood flour is mixed into the resin material, it has been pointed out that the inclusion of the filler causes embrittlement and low impact resistance. There is.

Therefore, various measures have been considered to reduce the weight of the seed base material as much as possible and to prevent the impact resistance from decreasing when reducing the weight, but there are no such solutions. At present, no fundamental solution has been found, or even if the weight can be reduced, the material cost is extremely high.

In addition, as a measure to reduce the weight, the use of foam as the material constituting the core material is being considered.

However, it is difficult to press or vacuum form such a foam sheet into a core material of the desired shape, and the air bubbles that make up the foam disappear due to the heat and pressure of the molding process. On the other hand, there are drawbacks such as air bubbles on the surface becoming punctured by heat or the like.

The present invention was made in view of the above background, and
This product provides a foamable composite resin sheet that causes a crosslinking reaction and foams during press molding or vacuum molding.Conversely, the sheet foams due to heat and pressure during molding, and the shape of the resin sheet is expanded. There are six kinds of -C, which can be solidified at 44 to form a core material, etc.

For this purpose, the present invention mixes 42 to 100 parts of a cellulose filler to 100 parts of a polyolefin resin base material selected from a blend of P p/p E or a random Aiike Prokkobo IJ-r-; 0.5 to 3 parts of radical generator 1 4 to 15 parts of blowing agent and 2 parts of crosslinking agent
, 5 to 20 parts, and is extruded in a non-crosslinked and unfoamed state.

To explain the present invention in more detail, the composite resin sheet is P P
/PE Blend or random or block copolymer selected polyolefin resin base material 10
0 parts to 42 to 100 parts of cellulose filler, and further 0, 5 to 3 parts of radical generator, 4 to 1.5 parts of blowing agent.
1 part and 2.5 to 20 parts of a crosslinking agent were added, and the composition was mixed uniformly with a mixer, and then put into an extruder K.
It is extruded into a plate shape at a resin temperature of 170 to 190°C.

When the above-mentioned foaming agent, radical generating agent, and crosslinking agent are kept at a resin temperature of 190° C. or less during the extrusion molding, the sheet can be produced in a state in which the above-mentioned foaming agent, radical generator, and crosslinking agent are uniformly mixed and dispersed in the above-mentioned composition in a non-crosslinked and non-foamed state. 11 is an intermediate product that can be handled in the same way as conventional molding sheets.

Next, more detailed material names of the above-mentioned components and reasons for limiting their mixing ratios will be explained.

First, as the polyolefin resin base material, a PP/PE blend or one selected from random or block copolymers is used.

In this case, polypropylene is industrially the cheapest material and is easily available in large quantities and stably, but it has high crystallinity and melting point, and also has radical generators and blowing agents.
It must have a very high decomposition point, and since homopolypropylene has a methyl group in the sonomolecule, it is decomposable when radicals are generated, and the main chain that makes up one molecule is easily broken, and crosslinks are easily formed. Blending PE ingredients due to difficulty
Alternatively, it is necessary to introduce it as a copolymer.

On the other hand, in PE, a cross-linking agent is not particularly required.
Required in P/P E blends or copolymers. Furthermore, the extrusion temperature can be lowered by introducing the PE component.

Next, wood powder such as wood chips is used as the cellulose filler, and the blending ratio of this and the resin base material is 100% of the resin base material.
It is pointed out that a sheet cannot be made smoothly at a blending ratio of 100 parts of wood flour to 100 parts of wood flour. i.e. wood flour 10
When the blend exceeds 0 parts, the flowability of the resin decreases, the residence time in the extruder increases, and the resin pressure also increases, causing a crosslinking reaction at the stage of producing an unreacted sheet.

Extrusion is often impossible, and if the amount is less than 42 parts, the resin component will be large, resulting in high costs.

Therefore, in the present invention, the effective range of wood flour content is 42 to 100.
This range also provides balanced FC product performance and productivity.

Next, the radical generating agent is a commonly used peroxide, more specifically, a radical generating function at a relatively high temperature such as cumene hydroperoxide. It is an initiator for crosslinking, and increases the viscosity of the resin base material by crosslinking in the pre-foaming stage, and uses this increase in viscosity to prevent defoaming.

In addition, at this time, as the resin base material, the above-mentioned -IP P/
When a blend or copolymer of PE is used, the reaction starts in the direction in which the molecular chain is cut.
It is necessary to add the above-mentioned crosslinking agents, such as divinyl pentene, diallyl phthalate, etc., to accelerate the reaction, and the composition of each of them is 0.5 to 3 parts of the radical generator per 100 parts of the resin base. A suitable composition ratio is 25 to 20 parts of crosslinking agent.

Next, adding 4 to 15 parts of a foaming agent to 100 parts of the resin base material will affect the apparent density during foam molding, which will be described later. When considering application to materials,
The apparent density in the product state is 0.2 to 0.
9 f/cy", and corresponding to this apparent density, the addition of blowing agent (1#t) is in the range of 12 to 15 parts. If this is exceeded, the apparent density becomes smaller and the stiffness decreases. On the other hand, if the amount is less than 4 parts, a uniform foamed state cannot be obtained and the weight becomes heavy, making it impossible to achieve the purpose of weight reduction.

Note that one blowing agent is azodicarbonamide.

Hydrazocarbonamide is mentioned, but in this case hydrazocarbonamide gives better results.

In other words, this material has heat resistance up to 241°C, which makes it possible to ensure an unfoamed state during extrusion molding of PP/PE blends or copolymers.
Since azodicarbonamide starts foaming at a lower temperature, hydrazocarboxylic acid amide is more advantageous in producing an unfoamed sheet.

The following materials are mixed and dispersed in a Henschel mixer in the above-mentioned composition ratio, and then extruded into a sheet by an extruder.

In this case, the extrusion molding conditions are preferably lower Vi and resin temperature in order to suppress decomposition or reaction initiation of the blowing agent and radical generator, but P/P E blend containing 742 to 100 parts of wood flour't In the case of wood or copolymers, the wood flour increases the viscosity, so the extrusion temperature u
The lower limit is 170° C. Below this, extrusion becomes impossible due to resin viscosity.

On the other hand, at temperatures above 190°C, the shear friction between the resin base material and wood flour in the fluidized state may cause partial high temperatures, and the decomposition of the radical generator or blowing agent may occur until the foaming temperature is reached. However, since the he reaction proceeds during extrusion, the foaming effect during the secondary molding process described later is small, so the extrusion temperature is limited to m1hi7o to 190°C.

Within this temperature range, a good foamable composite resin sheet can be continuously extruded.

Next, the use of the foamable composite resin sheet constructed as shown in E will be explained. This sheet has uses as a molding material for secondary forming processes such as press molding and vacuum forming.

As an example, in the case of press molding, the composite resin sheet described in (h) is trimmed in advance to form a product shape with predetermined dimensions in exactly the same way as conventional core material constituent materials, and at the stage prior to press molding, The surface change is over 20°C using an infrared heater.

That is, when heated to the temperature of the decomposition temperature plate of the foaming agent in the resin base material, the molten resin sheet becomes thickened due to the radical generator and crosslinking agent contained in the composite resin sheet, and then Foaming begins and the product expands. Next, the sheet in which this crosslinking reaction has progressed and is in the process of swelling is set between the molds of a cold press mold with a clearance of 1, and when these molds are engaged, the sheet described above is press-formed, Next, by cooling the mold, a foam core material having a curved surface that follows the mold surface shape of the mold is obtained.

The apparent density of the core material formed by press molding in this way is 0.2 to 0.9'f/cm s, depending on the mold clearance, which is higher than that of the conventional non-foamed molded core. It is extremely lightweight compared to wood, and
Its impact resistance will also be improved.

Incidentally, it goes without saying that vacuum forming can also be carried out in the same manner as conventional forming operations after heating in the preliminary stage.

Next, more specific embodiments of the present invention will be described. However, this invention is not limited to the following examples and can be modified in various ways.Example 1 An attempt was made to manufacture a foamable composite resin sheet using the blending ratios shown in the table below.

Table 1 (composition ratio) All numerical values are parts by weight.

matara radical generator ridge men hydroperoxide association,
Hydra Y carbonamide was used as a blowing agent, and divi♂bentone was used as a crosslinking agent.

These 41 to 6 formulations were mixed in a Henschel mixer and then extruded with extrusion flexibility as shown in Table 2 below. Also, for the formulation of Mu1, Vi, tq
Extrusion molding is performed at various fat temperatures and degrees, and the moldability of these,
The state when this was subjected to secondary processing was observed.

Table 2 As is clear from Table 1.2, the ratio of KPP/PE copolymer:wood flour is 100:42 to 1oo:toos.
Within this range, good extrusion moldability and good foamability can be obtained when the product is made into a secondary product.

Also 44. For those containing As, the amount of blowing agent and the amount of crosslinking agent can be reduced, but the foaming properties are reduced in both cases. This is because the former has a low foaming property, and the superior has a low crosslinking state in the pre-foaming stage, so it is defoamed.

Furthermore, in the formulation of Mu 1, the resin temperature during extrusion molding was changed, but no extrusion occurred at 165°C, and the temperature was 195°C.
Although good extrusion can be carried out at 10°C, a reaction starts at 17°C, making it impossible to produce a good secondary product. Therefore, the lower limit of the extrusion molding temperature t is 170°C, F.
The temperature is limited to 190℃.

Example 2 Based on the optimal results obtained in Example 1, the blending ratio of PP/PE random copolymer:wood flour was set to 70:30, and 1 part of cumene hydroperoxide as a radical generator and a blowing agent were added to the total amount of this copolymer. as hydrazocarbonamide 4
1 part and 2 parts of divinylbenzene as a crosslinking agent were mixed in a Henschel mixer, and extrusion molding was performed within the extrusion coloring temperature range described in E.

1.26mm thick unreacted sheet in 25-30 countries)? Created.

The extrusion moldability of this product is that of conventional polypropylene: wood flour 5
With a ratio of 0:50, it can be produced as well as a non-foamed resin sheet (hereinafter referred to as the current product).

Next, the surface temperature of this resin sheet was heated to 23℃ using an infrared heater.
Heated 2.5ml at 5°C (E below the foaming start temperature of the blowing agent), then placed it in a lower mold E with a clearance of t2.3mm, engaged the mold E with it, and press-molded it. I did it. Through this press molding, a core constituent material having uniform fine cells was obtained.

Next, Table 3 below shows comparative data on the physical properties of the product obtained by press processing the sheet according to the present invention obtained in this example (hereinafter referred to as the "invention product") and the current product. .

As is clear from Table 3 below, the tensile strength of the current product and the product of the present invention is 59% in the vertical direction and 53% in the horizontal direction.

In addition, the bending strength is 33% vertically and 45cm horizontally, and the 1 bending modulus is 31cm vertically and 45cm horizontally, which is about a 40% weight reduction compared to the current product, and the weight is reduced by about 40% compared to the current product. did not break at +21°C and 280 m, and at -20°C, the blending ratio of polypropylene:polyethylene:wood flour was 5.2.
5: 1.75: 3 (PP/PE is a blended product) and 100 parts of cumene hydropanioxia)'
0.75i, 1.5 parts of divinylbenzene, and 5 parts of hydrocarbonamide were added, and after mixing, an extruder was used to make the cell thickness 1.
A flat plate of mm was extruded.

This product has good extrusion moldability.

Next, the half sheet metal assembly was heated and foamed to a thickness of approximately 2.5 mm, and subsequently a molded product with a thickness of 2.0 mm was obtained using a trowel inside a press mold.

The surface condition of this foamed product was good. -1 Other physical properties are summarized in Table 4 below, and are noteworthy: (1) The decrease in tensile strength, bending strength, and strength is small.

(2) Impact resistance is approximately twice that of current products.

(3) Although the specific gravity is somewhat large, it shows superiority compared to current products.

There are advantages such as

Example 4 P P / P E : I polymer (PEn component 10% or less): polyethylene: wood flour = 6:1:3 blending ratio 10
0 parts, 1 part of cumene-on-drober oxide, 0.75 parts of divinylbenzene, 5 parts of hydrocarbonamide were added with a picture, and after mixing, a flat plate with a thickness of 1.0 mm was extruded using an extruder. 1. Then, after heating, it was pressed. A molded product fc) 4+ was molded to a thickness of 1.8 mm. The extrusion moldability of this product is good, and the surface condition of the press molded product is also good. The other physical properties V are shown together with Table 4 below, but are noteworthy.

(1) The specific gravity is 0.75, making it much lighter than current products.

(2) Impact resistance is approximately twice that of current products.

Contains advantages such as

Table 4

Claims (1)

[Claims] (1) 42 to 100 parts of a cellulose filler is mixed into 100 parts of a polyolefin resin base material selected from a blend of pp/PH or a random or block copolymer, and 0.5 to 3 parts of a radical generator. A foamable composite resin sheet containing 4 to 15 parts of a blowing agent and 2.5 to 20 parts of a crosslinking agent and extruded into a sheet in a non-crosslinked and unfoamed state.