JPH07119309B2 - Open-cell olefin resin foam composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin composition suitable for producing an open-cell type resin foam containing an olefin resin as a main component.

[Conventional technology]

Although olefin resin foams are mainly closed-cell foams, this foam is naturally unsuitable for applications requiring water absorption or air permeability.

Conventionally, as a method for producing an open-cell type olefin resin foam, a method is known in which a foam having closed cells is once produced and then the cell membrane is destroyed by heat expansion or pressure compression.

In this way, instead of performing continuous foaming and foaming in separate steps,
Japanese Patent Publication No. 60-49657 proposes a composition for an open-cell type ethylene-based resin foam suitable for producing an open-cell type olefin resin foam in one step.

This composition comprises 100 parts by weight of ethylene resin and 1 to 2 blowing agents.
The present invention is characterized in that 0.1 to 10 parts by weight of a trifunctional monomer and 0.1 to 5 parts by weight of silicone oil are added to a crosslinked foaming composition consisting of 0 parts by weight and 0.3 to 10 parts by weight of an organic peroxide as a crosslinking agent. .

[Problems to be solved by the invention]

The known composition reverses the relative relationship between the decomposition temperature of the foaming agent and the decomposition temperature of the cross-linking agent as compared with the conventional foaming technique, and the addition of a small amount of a trifunctional monomer and silicone oil reduces the bubble diameter before and after the foam breaking. By making it fine and highly uniform,
It is assumed that a uniform and fine open cell body can be obtained.

By the way, the dimethyl silicone oil, which is widely known as a silicone oil, used in this composition has poor compatibility with an olefin resin and is very difficult to knead. Therefore, this composition has drawbacks such that foaming is not stable, bubbles are rough, and setting of foaming conditions is limited. Also, the trifunctional monomer added at the same time in this composition is liable to bleed after addition,
Often there was the drawback of adversely affecting the life of the kneaded composition.

The present invention aims to solve the above-mentioned problems.

[Means for solving problems]

The open-cell type olefin resin foam composition of the present invention comprises 100 parts by weight of an olefin resin, 1 to 20 parts by weight of a foaming agent, and 0.1 to 10 parts by weight of an α-olefin modified silicone oil represented by the following formula (1). The melt index of the olefin resin is 5 to 30, and the foaming agent has a decomposition starting temperature in the range of 100 to 160 ° C. and is 20 to 70 ° C. higher than the melting point of the olefin resin. And the decomposition completion temperature of the foaming agent is 150 to 210 ° C., and the α-olefin modified silicone oil has a carbon number of α-olefin of 4 to 20 and a modification rate by α-olefin of 20 to 80%. Is characterized in that.

Here, the olefin resin is a polymer such as medium- and low-pressure polyethylene, high-pressure polyethylene, linear low-density polyethylene (linear low density polyethylene; LLDPE), ultra-low-density polyethylene, or a polymer containing ethylene as a main component. For example, a copolymer such as an ethylene-vinyl acetate copolymer, an ethylene-propylene copolymer, an ethylene-α olefin copolymer, or a mixture of two or more kinds of these polymers is used.

In addition, these olefin resins are melt index (according to ASTM-D1238, hereinafter sometimes referred to as MI).
Of 5 to 30 are preferable, and those of 5 to 20 are particularly preferable. This is because if the MI is less than 5, the closed cell ratio tends to increase, and if it exceeds 30, the bubbles tend to flow laterally during foaming. It is possible to mix two or more kinds of olefin resins and use the MI of the mixed resin within the above range, but in that case, it is preferable to mix and use the same kind of resin.

Further, as the foaming agent, for example, azobisisobutyronitrile, azodicarbonamide, P-toluenesulfonyl hydrazide, dinitrosopentamethylenetetramine,
4,4′-oxybisbenzenesulfonyl hydrazide and the like are used, and among them, azodicarbonamide is particularly preferably used, and the compounding amount thereof is in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the olefin resin. Is appropriate, and the amount used is appropriately determined within this range from the target expansion ratio and the amount of gas generation of the foaming agent used.

This foaming agent has a decomposition starting temperature in the range of 100 to 160 ° C. and a melting point of the olefin resin of 20 to 70 ° C.
And the decomposition completion temperature of the foaming agent is 150 to 2
A temperature of 10 ° C is used. If the decomposition starting temperature is less than 100 ° C, it is difficult to process, foaming gas easily escapes and it is difficult to generate bubbles, and if it exceeds 160 ° C, the viscosity of the resin cannot be balanced and the generated gas is not generated. Since the molten resin wall is broken and the generated bubbles cannot be held and the bubbles become coarse, it cannot be adopted. Further, if the decomposition start temperature is less than the melting point of the ethylene resin used + 20 ° C, the viscosity of the resin cannot follow the foaming and the gas easily escapes from the resin wall, and the melting point of the olefin resin used exceeds 70 ° C. If so, the resin will flow and bubble generation will not be successful.

Incidentally, the above temperature condition range is often difficult to satisfy with a single foaming agent, so urea compounds, zinc oxide,
It is desirable to add 1 to 10 parts by weight of a decomposition accelerator such as a zinc compound or a lead compound to adjust the temperature condition range.
Further, if necessary, two or more kinds of foaming agents can be used in combination, and this is rather preferable.

The decomposition start temperature and the decomposition completion temperature refer to each point of the temperature-time curve when measured at a temperature rising rate of 10 ° C./min on a differential thermal balance, and the decomposition start temperature is the temperature at the rising point thereof. The completion temperature is its peak point.

The α-olefin modified silicone oil used in the present invention is modified with α-olefin having 4 to 20 carbon atoms, and the modification rate is 20 to 80%, preferably 30 to 70%.

The modification rate with α-olefin in the present invention is calculated by the following formula.

Modification rate with α-olefin (%) = 100 × n / (m + n) This α-olefin-modified silicone oil has good compatibility with olefin resins, little bleeding from the kneaded product, and is effective as a surfactant. Stable performance, 0.1 to 10 parts by weight per 100 parts by weight of olefin resin.
It is compounded in the range of parts by weight. If it is less than 0.1 parts by weight, the effect cannot be expected sufficiently, and if it exceeds 10 parts by weight, the effect is not increased and it is uneconomical, and problems such as bleeding easily occur, which is not preferable.

Like the conventional foamable composition, the composition of the present invention may be added with a heat stabilizer, an antioxidant, an ultraviolet stabilizer, an inorganic filler, a pigment, a flame retardant or other additives, if necessary. .

The composition of the present invention is formed into pellets, powders, films, sheets, etc. by heating and foaming into desired foams, which are usually heated by means of hot air, infrared heaters, high-frequency heating, etc. It is performed at 250 ° C. The heating at this time is preferably carried out rapidly up to the foaming start temperature of the foaming agent, and thereafter slowly heated, and it is desirable to cool (50 ° C. or less) after foaming to fix the cell structure.

[Action]

In this invention, the MI of the olefin resin is as described above, and the foaming agent is made of α-olefin modified silicone oil having a specific decomposition temperature region as described above and having good affinity with the olefin resin. Since it is the foamable composition as described above, the viscosity of the olefin resin, the timing of decomposition of the foaming agent, and the foam stabilizing effect of the α-olefin-modified silicone oil are combined to eliminate the cross-linking of the resin by the chemical cross-linking agent. In addition, while maintaining the fine cell structure, the cell breakage will progress, and in the stage of the heating and foaming process, the cell structure will not be crushed or collapsed, and the bubble diameter will be fine and continuous cell type foam with high uniformity. The body is obtained.

〔Example〕

Example 1 100 parts by weight of ethylene-vinyl acetate copolymer having MI of 7.0 and 6% by weight of vinyl acetate (melting point: 101 ° C.), 10 parts by weight of azodicarbonamide, 3 parts by weight of urea and 2 parts by weight of zinc oxide, α Olefin modified silicone oil (50% by C ₁₀ H ₂₀
2 parts by weight was kneaded with a mixing roll having a surface temperature of 110 ° C. for about 5 minutes. The decomposition start temperature of azodicarbonamide in this kneaded product was 140 ° C, and the decomposition completion temperature was 1 ° C.
It was 63 ° C.

Then, this kneaded product was pressed with a press molding machine at 115 ° C to a thickness of 1.0.
It was formed into a sheet of mm. When this sheet was placed on a Teflon sheet and heated in an oven at 190 ° C for about 4 minutes,
Foamed uniformly. Then, the foamed sheet obtained by cooling at room temperature for 10 minutes is a pure white soft and flexible open-cell body, an apparent density of 0.05 g / cm ³ , a cell diameter of 0.2 to 0.3 mm,
The closed cell rate was almost 0%.

Example 2 A foamed sheet obtained in the same manner as in Example 1 except that an ethylene-vinyl acetate copolymer having an MI20 content of 28% and a vinyl acetate content of 28% was used. The apparent density was 0.052 g / cm ³ , and the cell diameter was Is
It was 0.15 to 0.25 mm, the closed cell ratio was almost 0%, and it was pure white and very soft to the touch.

Example 3 Low density polyethylene having MI of 9.0 and density of 0.917 (melting point: 109
100 parts by weight, 10.5 parts by weight of azodicarbonamide, 2 parts by weight of urea and 2 parts by weight of zinc oxide, 2 parts by weight of α-olefin modified silicone oil (70% modification rate by C ₁₀ H ₂₀ ) at a surface temperature of 120 ° C. The mixture was kneaded with a mixing roll for about 5 minutes. The decomposition initiation temperature of azodicarbonamide in this kneaded product was 143 ° C, and the decomposition completion temperature was 163 ° C.

Then, this kneaded product was pressed to a thickness of 1.0 with a press molding machine at 125 ° C.
It was formed into a sheet of mm. When this sheet was placed on a Teflon sheet and heated in an oven at 190 ° C for about 4 minutes,
Foamed uniformly. Then, it was cooled at room temperature for 10 minutes to obtain a pure white foamed sheet. This foamed sheet had a thickness of 19 mm, an apparent density of 0.05 / cm ³ , a cell diameter of 0.2 to 0.3 mm, and a closed cell ratio of almost 0%.

Example 4 Low density polyethylene having MI23 and a density of 0.916 (melting point 1
The foamed sheet obtained in the same manner as in Example 3 except that the temperature was set to 09 ° C.) was 18 mm in thickness, the apparent density was 0.053 g / cm ³ , the cell diameter was 0.2 to 0.3 mm, and the closed cell ratio was almost 0%. It was a pure white open cell.

Example 5 Low density polyethylene having MI of 10 and density of 0.905 (melting point: 109 ° C)
100 parts by weight, 8 parts by weight of azodicarbonamide, 3 parts by weight of urea and 2 parts by weight of zinc oxide, 2 parts by weight of α-olefin modified silicone oil (70% modification rate by C ₁₃ H ₂₆ ) are mixed with a surface temperature of 120 ° C. And kneaded for about 7 minutes. The decomposition initiation temperature of azodicarbonamide in this kneaded product was 143 ° C, and the decomposition completion temperature was 163 ° C.

Then, this kneaded product was pressed to a thickness of 1.0 with a press molding machine at 125 ° C.
It was formed into a sheet of mm. When this sheet was placed on a Teflon sheet and heated in an oven at 190 ° C for about 5 minutes,
Foamed uniformly. Then, it was cooled at room temperature for 10 minutes to obtain a slightly yellowish white foamed sheet. This foam sheet has a thickness of 13.5 mm, an apparent density of 0.07 g / cm ³ , and a cell diameter of
It was 0.25 to 0.35 mm, and the closed cell ratio was almost 0%.

Example 6 The unfoamed molded sheet of Example 2 was placed on a Teflon sheet, placed in a microwave oven for cooking preheated to 150 ° C., and heated at high frequency to uniformly foam for 2 minutes. When this foamed sheet was taken out and cooled to room temperature, Example 2
It was a foam similar to that obtained in.

Example 7 MI of 8 and linear low density polyethylene of 0.920 density (melting point 126
100 parts by weight, 8 parts by weight of azodicarbonamide, 1 part by weight of urea and 2 parts by weight of zinc oxide, 2 parts by weight of α-olefin modified silicone oil (70% modification rate by C ₁₃ H ₂₆ ) at a surface temperature of 135 ° C. The mixture was kneaded with a mixing roll for about 7 minutes.
The decomposition initiation temperature of azodicarbonamide in this kneaded product was 152 ° C, and the decomposition completion temperature was 170 ° C.

Then, this kneaded product was pressed at a temperature of 135 ° C. to a thickness of 1.0.
It was formed into a sheet of mm. When this sheet was placed on a Teflon sheet and heated in an oven at 190 ° C for about 5 minutes,
Foamed uniformly. Then, it was cooled at room temperature for 10 minutes to obtain a slightly yellowish white foamed sheet. This foam sheet has a thickness of 13.5 mm, an apparent density of 0.07 g / cm ³ , and a cell diameter of
It was 0.3 to 0.4 mm and the closed cell ratio was almost 0%.

Comparative Example 1 MI 4.0, 100 parts by weight of ethylene-vinyl acetate copolymer having a vinyl acetate content of 14% by weight (melting point 89 ° C.), 8 parts by weight of azodicarbonamide, 3 parts by weight of urea and 2 parts by weight of zinc oxide, α Olefin modified silicone oil (70% with C ₁₃ H ₂₆
2 parts by weight were mixed with a mixing roll having a surface temperature of 110 ° C. for about 6 minutes. The decomposition start temperature of azodicarbonamide in this kneaded product was 143 ° C, and the decomposition completion temperature was 1
It was 63 ° C.

Then, this kneaded product was pressed by a press molding machine at 120 ° C to a thickness of 1.0.
It was formed into a sheet of mm. When this sheet was placed on a Teflon sheet and heated in an oven at 190 ° C for about 4 minutes,
It was foamed but wavy. Then, the foamed sheet obtained by cooling at room temperature for 10 minutes had a cell diameter of 0.2 to 0.3 mm, but large corrugations remained as it was, and it was not a practical foam. It is considered that this is because the viscosity of the resin at the time of foaming is high, resulting in a three-dimensional foaming and a waviness phenomenon.

Comparative Example 2 The same results as in Comparative Example 1 except that an ethylene-vinyl acetate copolymer having an MI2 content and a vinyl acetate content of 25% was used. No foamed sheet was obtained.

Comparative Example 3 100 parts by weight of ethylene-vinyl acetate copolymer having MI of 41 and vinyl acetate content of 41% by weight (melting point 70 ° C.), 8 parts by weight of azodicarbonamide, 3 parts by weight of urea and 2 parts by weight of zinc oxide, α Olefin modified silicone oil (70% with C ₁₃ H ₂₆
2 parts by weight were mixed with a mixing roll having a surface temperature of 110 ° C. for about 6 minutes. The decomposition start temperature of azodicarbonamide in this kneaded product was 143 ° C, and the decomposition completion temperature was 1
It was 63 ° C.

Then, this kneaded product was pressed with a press molding machine at 110 ° C. to a thickness of 1.0.
It was formed into a sheet of mm. This sheet was placed on a Teflon sheet and heated in an oven at 180 ° C. for about 4 minutes to foam. Then, the foamed sheet obtained by cooling at room temperature for 10 minutes had a cell diameter of 0.2 to 0.4 mm, a difference in cell diameter depending on the portion, and a thickness of 10 mm, and a practical foam could not be obtained. This is probably because the lateral flow of the resin during foaming is large.

〔The invention's effect〕

Since the present invention is the foamable composition as described above,
The viscosity of the olefin resin, the timing of the decomposition of the foaming agent, and the foam-regulating effect of α-olefin modified silicone oil combine to maintain the fine cell structure even when the resin is not crosslinked by a chemical crosslinking agent, Will progress,
In the stage of the heat-foaming step, an open-cell type foam having a fine cell diameter and a high uniformity can be obtained without the cell structure being crushed or collapsed. If no chemical cross-linking agent is used, there is no fear of coloring or discoloration.

Further, this foam composition is suitable not only for a batch-type production method but also for an endless-type production of an atmospheric pressure or open type foam.

Further, when this composition is used, an olefin resin foam having excellent water absorption, air permeability, weather resistance, flexibility, and feeling can be obtained.

Claims (1)

[Claims] 1. An olefin resin 100 parts by weight, a foaming agent 1-2.
0 parts by weight, 0.1 to 10 parts by weight of α-olefin modified silicone oil represented by the following formula (1), the melt index of the olefin resin is 5 to 30, and the foaming agent has a decomposition start temperature. Is in the range of 100 to 160 ° C. and is 20 to 70 ° C. higher than the melting point of the olefin resin, and the decomposition completion temperature of the foaming agent is 150 to 210 ° C., and the α-olefin-modified silicone oil is further added. Is an open-cell type olefin resin foam composition, wherein the α-olefin has 4 to 20 carbon atoms and the modification rate with the α-olefin is 20 to 80%. (R: saturated hydrocarbon having 4 to 20 carbon atoms)