JPH04103642A - Composition for polypropylene crosslinked form - Google Patents

Abstract

PURPOSE:To obtain the title composition containing a propylene--nonconjugated diene copolymer containing a non-conjugated diene of a specific amount and foaming agent, and capable of providing a foam having a feeling of smooth touch without impairing the mechanical and heat resistant characteristics of PP. CONSTITUTION:The objective composition containing (A) (i) propylene-- nonconjugated diene copolymer containing 0.2-10wt.% non--conjugated diene (preferably 1,4-hexadiene) and (ii) homogeneous polypropylene and/or propylene- ethylene random copolymer containing <=4wt.% ethylene content and (B) foaming agent (e.g. azodicarbonamide) of 1-30 pts.wt. based on 100 pts.wt. total of these components i+ii and being <=80% in the content of the component ii and >=0.2% in the above-mentioned non-conjugated diene content when total of these components i+ii is 100%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composition for crosslinked polypropylene foam, and in particular to a composition for a crosslinked polypropylene foam that has a smooth feel without substantially impairing the mechanical properties and heat resistance characteristic of polypropylene. The present invention relates to a composition for a crosslinked polypropylene foam that provides a polypropylene foam.

[Prior art and problems to be solved by the invention] Polyolefin foams have excellent mechanical strength, flexibility, texture, heat resistance, chemical resistance, etc., and are used as interior materials for automobiles, insulation materials,
It is widely used in cushioning materials for sporting goods and food packaging, as well as other sound-deadening materials and exterior materials.

Among them, polyethylene foam has a low melting point and is therefore flexible.
Excellent texture, elongation, etc. On the other hand, polypropylene foam has excellent mechanical strength such as tensile strength and bending strength, and heat resistance. Usually, as such polypropylene, a propylene-ethylene random copolymer is used.

However, compared to polyethylene resins, polypropylene resins tend to have larger and non-uniform foam cells and are less flexible. For this reason, there is a problem in that the resulting foam is hard, brittle, and has a smooth feel.

In order to improve this problem with polypropylene resins, foam compositions containing a blend of propylene-ethylene random copolymer and linear low-density polyethylene in an amount of about 30 to 50% by weight are commercially available. However, there is a problem in that both the mechanical strength and heat resistance, which are the characteristics of polypropylene, and the feel to the touch have not been improved to a satisfactory level.

Therefore, an object of the present invention is to provide a composition for crosslinked polypropylene foam that provides a foam with a smooth feel without substantially impairing the mechanical properties and heat resistance specific to polypropylene.

[Means to solve the problem]

In view of the above issues, as a result of intensive research, the present inventors discovered that the deterioration in the physical properties and feel of propylene resin foams is due to deterioration during crosslinking, and that it is possible to suppress this deterioration to the minimum level. The inventors discovered that it is sufficient to use a propylene resin prepared by copolymerizing a small amount of non-conjugated diene, and came up with the present invention.

That is, the first composition for a crosslinked polypropylene foam of the present invention contains 0.2 to 10.0% by weight of fa) nonconjugated diene.
a propylene-nonconjugated diene copolymer containing (b)
1 to 30 parts by weight per 100 parts by weight of the propylene copolymer
It is characterized by containing parts by weight of a blowing agent.

Further, the second composition for a crosslinked polypropylene foam of the present invention comprises fa) (i) a propylene-nonconjugated diene copolymer containing 0.2 to 10% by weight of a nonconjugated diene;
D homopolypropylene and/or propylene-ethylene random copolymer with an ethylene content of 4% by weight or less;
b) Contains 1 to 30 parts by weight of a blowing agent based on the total of 100 parts by weight of (i) and (ii) above, and the total of (1) and (ii) above is 100% by weight. 0(i
The content of ii) is 80% by weight or less, and the content of the non-conjugated diene is 0.2% by weight or more.

The third composition for polypropylene crosslinked foam of the present invention is:
(a+ (i) 0.2 to 10.0% by weight of non-conjugated diene
a propylene-nonconjugated diene copolymer containing, (ii
i) linear low-density polyethylene, and (bl) 1 to 30 parts by weight of a blowing agent based on a total of 100 parts by weight of (i) above (iii),
) The above (iii) is taken as 100% by weight, and the above (ii)
i) The content of linear low density polyethylene is 50% by weight or less.

Furthermore, the fourth composition for polypropylene crosslinked foam of the present invention contains fa) (i) a non-conjugated diene of 0.2 to 10.0;
a propylene-nonconjugated diene copolymer containing % by weight;
(ii) homopolypropylene and/or a propylene-ethylene random copolymer with an ethylene content of 4% by weight or less; (iii) linear low-density polyethylene; (b) the above (i) above (ii) above ( Contains 1 to 30 parts by weight of a blowing agent per 100 parts by weight of iii), and the content of GD is 80% by weight when the total of (i) and (ii) is 100% by weight. and the content of the non-conjugated diene is 0.2% by weight or more, and the content of the zero-linear low density polyethylene is
) is characterized by being 50% by weight or less excluding 100% by weight of (iii) above.

The present invention will be explained in detail below.

In the present invention, (i) a propylene-nonconjugated diene copolymer is used as the resin component (al) of the composition for a crosslinked polypropylene foam.

The above (i) propylene-nonconjugated diene copolymer refers to propylene with the following formula (wherein R2-R4 are H or an alkyl group having 1 to 6 carbon atoms, and n is 1 to 2 (iii)). It is obtained by random polymerization or graft polymerization of non-conjugated diene comonomers represented by (representing an integer).

Examples of the non-conjugated diene include 2-methyl-1,
4-pentadiene, 1,4-hexadiene, 4-methylidene-1-hexene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,4-hebutadiene, 4-ethyl -1,4-hexadiene, 4,5
-dimethyl-1,4-hexadiene, 4-methyl-1,
4-hebutadiene, 4-ethyl-1,4-hebutadiene, 5-methyl-1゜4-hebutadiene, 5-methyl-1
, 4-octadiene, 1.5-heptadiene, 1.5-
Octadiene, 5-methyl 1,5-heptadiene, 6-
Methyl-1,5-heptadiene, 2-methyl-1,5-
hexadiene, 1,6-octadiene, 6-methyl-1
, 6-octadiene, 7-methyl-16-octadiene, 2-methyl-1,6-hebutadiene, 1,9-decadiene, 1,13-tetradecadiene, and the like.

Among these, 1,4-hexadiene, 2-methyl-1,4-pentadiene, 1,9-decadiene and the like are particularly preferred. Two or more of these non-conjugated diene comonomers can also be used in combination.

To randomly copolymerize propylene and a nonconjugated diene comonomer, a conventional copolymerization method using a Ziegler-Natsuta catalyst may be applied. In this case, the proportion of the non-conjugated diene is adjusted to be 0.2 to 10% by weight. If the content of non-conjugated diene is less than 0.2% by weight, the crosslinking efficiency is not sufficiently high and the effect of suppressing deterioration during crosslinking is not sufficient. Moreover, if it exceeds 10% by weight, the crystallinity of the copolymer will be significantly reduced. The preferred content of non-conjugated diene is 0.5 to 5% by weight.

Further, in order to graft-polymerize propylene and a non-conjugated diene comonomer, a method such as a solution method or a melt-kneading method may be used. In the case of melt mixing method, polypropylene, non-conjugated diene and catalyst are put into an extruder or twin-screw kneader,
What is necessary is just to heat it to the temperature of -250 degreeC and knead|mix while melting. In the case of a solution method, the starting material may be dissolved in an organic solvent such as xylene and stirred at a temperature of 80 to 140°C. In this case, the proportion of the non-conjugated diene is set to 0.2 to 10% by weight, as in the case of random polymerization described above.

As the above-mentioned propylene-nonconjugated diene copolymer, a graft copolymer is particularly preferable because the side chain diene moiety is an effective crosslinking reaction site.

In addition, propylene copolymer contains ethylene, butene-1
Other unsaturated monomers such as 5 mole % or less may be copolymerized. Further, the melt flow rate of this copolymer is usually within the range of 1 to 1000 g/10 minutes.

Further, in the present invention, the above (i) is used as the resin component (a).
) a propylene-nonconjugated diene copolymer and (ii) a homopolypropylene or propylene-ethylene random copolymer can be used.

In the present invention, homopolypropylene is a homopolymer of propylene, and usually has a melt flow rate of 1 to 50 g/10 minutes.

The melt flow rate of the above homopolypropylene is Ig/
If the time is less than 10 minutes, the formability of the sheet is insufficient;
If it exceeds 0 g/10 minutes, the mechanical strength will decrease, which is not preferable. A more preferable melt flow rate is 2 to 40.
g/10 minutes.

Also, the propylene-ethylene random copolymer (■) is
It is a product obtained by randomly copolymerizing repeating units derived from propylene and repeating units derived from ethylene, and usually has a melt flow rate of 1 to 50 g/10 minutes.

If the melt flow rate of the propylene-ethylene random copolymer is less than Ig/10 minutes, the moldability of the sheet will be insufficient, while if it exceeds 50 g/10 minutes, the mechanical strength of the composition will decrease. A more preferable melt flow rate is 2 to 40 g/10 minutes.

The ethylene content in such a propylene-ethylene random copolymer is 4% by weight or less, preferably 0.5% by weight or less.
It is 5 to 3.6% by weight. When the ethylene content in the propylene-ethylene random copolymer exceeds 4% by weight,
Mechanical strength at high temperatures, heat resistance, and secondary processability such as cutting and molding are reduced.

The blending ratio of (i) homopolypropylene and/or propylene-ethylene random copolymer as described above is (i)
It is 80% by weight or less, preferably 10 to 60% by weight, including 100% by weight of i). (ii) If the content of homopolypropylene and/or propylene-ethylene random copolymer exceeds 80% by weight, the crosslinking efficiency of the composition will not be sufficiently high and the effect of suppressing deterioration during crosslinking will not be sufficient.

However, in the present invention, the blending ratio of (ii) homopolypropylene and/or propylene-ethylene random copolymer not only satisfies the conditions in the above range, but also (i)
It is necessary to set the content of non-conjugated diene to be 0.2% by weight or more, assuming that the total of 10 GD is 100% by weight.

If the content of non-conjugated diene in the total of (i) + (ii) is less than 0.2% by weight, the crosslinking efficiency is not sufficiently high and the effect of suppressing deterioration during crosslinking is not sufficient.

The preferred content of non-conjugated diene is 0.5 to 5% by weight.

Furthermore, in the present invention, as the resin component (a), (i) propylene-nonconjugated diene copolymer (or ω propylene-nonconjugated diene copolymer), (ii) homopolypropylene and/or propylene-ethylene random (iii) linear low-density polyethylene can be used.

In the present invention, the ω-linear low-density polyethylene is a linear copolymer of ethylene and a olefin having 4 to 8 carbon atoms. Examples of the above-mentioned secondary olefin include 4-methylpentene-ISl-butene and 1-hexene. Further, the content of ethylene in the linear low density polyethylene is 90 mol% or more, preferably 95 mol% or more. Such linear low density polyethylene is usually 0
．． 9] Density of 0 to 0.940 g/crl and 0.7 to
0.940 minute melt index (old, JISK72
10, load 2.16 kg, 190″C).

The blending amount of such linear low density polyethylene is (i)
+Cth) (or (i) + (ii) ± (iii))
It is 50% by weight or less, preferably 20 to 30% by weight, assuming the total of 100% by weight. (iii) If the amount of linear low-density polyethylene exceeds 30% by weight, the mechanical strength, heat resistance, high-temperature properties, etc., which are the characteristics of polypropylene resins, will not be sufficient.

In the present invention, the blowing agent (b) is a compound that is liquid or solid at room temperature, but decomposes or vaporizes when heated above the melting point of the resin component, and is used for molding such as sheeting and crosslinking. Any decomposition temperature can be used as long as it does not substantially interfere with the decomposition temperature of 180 to 270°C.

Specific examples thereof include azodicarbonamide, azodicarboxylic acid metal salt, dinitrosopentamethylenetetramine, hydrazodicarbonamide, p-toluenesulfonyl semicarbazide, S-)lyhydrazinotriazine, and the like. These blowing agents contain a resin component (al (
(i), (i) + (ii), (i) 100, or (i
) + (ii) + (iii) 1 for 00 parts by weight per month
It is used in a range of 30 parts by weight, and the mixing amount can be changed as desired depending on the type and expansion ratio.

In the present invention, in addition to the above-mentioned blowing agent, a peroxide can be added to carry out a crosslinking reaction.

However, when the crosslinking reaction is carried out using ionizing radiation, it is not necessary to use an organic peroxide. When using an organic peroxide, it is preferably at a decomposition temperature of about 150°C or higher;
A specific example is methyl ethyl ketone peroxide (
182°C), t-butyl baroxyisobrovyl carbonate (153°C), dicumyl peroxide (171°C),
), cumene hydroperoxide (255°C), 2.
5-dimethyl-2,5-di(t-butylperoxy)hexane (179°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (179°C),
t-butylperoxy)hexyne-3 (193°C).

Di-t-butyl peroxyphthalate (159°Cχ) These organic peroxides are resin component (a) 1
It is used in a proportion of 0.01 to 1.0 parts by weight, preferably 0.05 to 0.5 parts by weight.

Further, in order to carry out the crosslinking reaction smoothly and efficiently, it is preferable to add a crosslinking aid. Examples of crosslinking aids that can be used in the present invention include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol pentaacrylate, diallyl phthalate, diallyl maleate, and the like. The amount of the crosslinking auxiliary agent added was 0.000 parts per 81100 parts by weight of the resin component.
The amount is 5 to 7.0 parts by weight, preferably 1.0 to 4.0 parts by weight.

In addition, in the present invention, various other compounding agents, specifically rubber substances, other resins, pigments, various fillers, flame retardant substances, oxidation An inhibitor and the like can be appropriately mixed.

Next, a method for producing a polyolefin crosslinked foam using a composition consisting of the above-mentioned components will be described.

First, the resin component (a) as described above, the blowing agent (1)),
and organic peroxides and crosslinking aids, which are blended as necessary.
Other ingredients are kneaded using a kneader, Henschel mixer, extruder, etc. At this time, it is necessary that the melt-kneading temperature be lower than the decomposition temperature of the blowing agent. The preferred melt-kneading temperature is 160 to 180°C.

Thereafter, the mixed material is extruded from a die such as an extruder and formed into a molded article such as a sheet. At this time, set the temperature of the dice to 16
It is preferable to control the temperature within the range of 5 to 175°C.

The molded body thus obtained is then crosslinked,
As for the formation method of the crosslinked structure, in addition to the method using organic peroxide as mentioned above, there are conventional methods such as irradiation with ionizing radiation such as alpha rays, beta rays (electron beams), and γ rays, and methods using heating. The method described can be adopted. Among these methods, a method by irradiation with ionizing radiation is preferred, and crosslinking by electron beam irradiation is particularly preferred. The amount of radiation irradiated varies depending on the type and amount of organic peroxide and crosslinking aid, and the degree of crosslinking, but is generally 1 to 30 Mrad.
, preferably 2 to 12 Mrad.

In addition, the composition for polypropylene crosslinked foam of the present invention is
Because the crosslinking efficiency is extremely high, crosslinking can be performed under conditions that are more relaxed than those of conventional polypropylene resins at the same gel fraction and expansion ratio (for example, when crosslinking is performed by irradiation with ionizing radiation, it is possible to perform crosslinking at a lower dose). cross-linking is possible).

The thus crosslinked polypropylene crosslinked foam composition is foamed at a temperature higher than the melting point of the resin component, preferably 230°C or higher, more preferably 240 to 270°C.
This can be done by heating to a temperature of The heating time required for foaming is usually 0.5 to 5 minutes.

[For production]

The composition for a crosslinked polypropylene foam of the present invention contains a propylene-nonconjugated diene copolymer as a resin component, and the content of the nonconjugated diene in the composition is within a specific range. With such a composition, a foam having a smooth feel can be formed without substantially impairing the mechanical properties and heat resistance characteristic of polypropylene.

The reason why such an effect is obtained is not necessarily clear, but propylene-nonconjugated diene copolymer has excellent heat resistance and high crosslinking efficiency, so when it is made into a composition, it can be used under milder conditions than usual. Can be cross-linked with
(For example, in the case of crosslinking by irradiation with ionizing radiation,
This is thought to be because crosslinking is possible at a low dose), and therefore deterioration associated with crosslinking can be suppressed to a minimum.

〔Example〕

The present invention will be explained in more detail by the following specific examples.

In each of the Examples and Comparative Examples, the following resins were used as raw material resins.

[11 Propylene-nonconjugated diene graft copolymer/P
PDM■: [Diene component = 2-methyl-1.4-pentadiene (C9), diene content 0.7% by weight, melt flow rate (MFR230°C, 2,16kg load) 0.7 g/10 minutes]・PPDM ■: [Diene component: l, 9 decadiene (C,.), diene content 1.1
Weight%, melt flow rate 1.0 g/10 min] ・PPDM ■: [Diene component = 1,9 decadiene (C
,. ), diene content 3.8% by weight, melt flow rate) 0.8 g/10-min] ]2] Propylene-ethylene random copolymer/RPP
■: [Ethylene content 0.4% by weight, melt flow rate 14 g/10 min] ・RPP■: [Ethylene content 2.6% by weight, melt flow rate 9mm ZlO] ・RPP■: [Ethylene content Amount: 3.6% by weight, melt flow rate: 9 g/10 min] [31 Linear low-density polyethylene/LLDPE■; [Melt index (Ml, 1
90°C2, 16kg load) 2g/10 minutes, density 0.9
26g/Ci) ・LLDPE■: [Melt index (Ml, 1
90°C2, 16kg load) 6g/lo min, density 0.9
15 g/cnf) Examples 1 to 9 and Comparative Examples 1 to 4 The blending ratio shown in Table 1 was 100 parts by weight of a resin component consisting of a propylene-nonconjugated diene copolymer and a propylene-ethylene random copolymer. To this, 15 parts by weight of a blowing agent, 1.5 parts by weight of a crosslinking aid, and 0.5 parts by weight of an antioxidant were added, and the mixture was mixed at 500 rpm using a Henschel mixer.
After mixing for 2 minutes at
It was extruded and pelletized at °C.

The pellets were fed to a sheet molding machine, and the extrusion temperature was 170.
A sheet with a thickness of 1.0 mm was produced by extrusion at °C.

Next, this sheet was irradiated with an electron beam at a dose shown in Table 1 to effect crosslinking. Thereafter, the foam was placed in an air oven at 250° C. for 2 minutes to decompose the foaming agent and foamed to about 25 times its original size.

For each cross-linked foam sheet obtained in this way, gel fraction, expansion ratio, tensile strength at break and elongation at break at 23°C, tensile strength at break and tensile elongation at high temperature (130°C), respectively. It was measured. In addition, the feel of the surface of the crosslinked foam sheet was evaluated.

The results are shown in Table 1 along with the composition and diene content in the polypropylene resin (propylene non-conjugated diene copolymer and/or propylene-ethylene random copolymer).

Examples 10 to I2 and Comparative Example 5.6 Propylene-nonconjugated diene copolymer, propylene-ethylene random copolymer, and
To 100 parts by weight of a resin component consisting of linear low density polyethylene, 15 parts by weight of a blowing agent, 1.5 parts by weight of a crosslinking aid, and 0.5 parts by weight of an antioxidant were added, and a Henschel mixer was added. After mixing for 2 minutes at 500 rpm, the mixture was fed to an extruder, extruded at an extrusion temperature of 170°C, and pelletized.

This pellet was fed to a sheet forming machine, and the extrusion temperature was 170.
°C and extruded to create a sheet with a thickness of 1.0 mm.

Next, this sheet was irradiated with an electron beam at a dose shown in Table 1 to effect crosslinking. Thereafter, the foam was placed in an air oven at 250° C. for 2 minutes to decompose the foaming agent and foamed to about 25 times its original size.

For each crosslinked foam sheet obtained in this way, gel fraction, expansion ratio, tensile strength at break and tensile elongation at break at 23°C, tensile strength at break and tensile elongation at high temperature (130°C), respectively. It was measured. In addition, the feel of the surface of the crosslinked foam sheet was evaluated.

The results are shown in Table 1 along with the composition and diene content in the polypropylene resin (propylene-nonconjugated diene copolymer and/or propylene ethylene random copolymer).

(This is a value measured according to IIJIS K6767, and shows the average value in the longitudinal direction (MD)/width direction (TD), respectively.

(This is a value measured according to 21 JIS K6767, and shows the average value in the longitudinal direction (MD)/width direction (TD), respectively.

(3) The surface feel of the crosslinked foam sheet was evaluated as ◎ if it was extremely smooth, 0 if it was smooth, △ if it was a little lacking in smoothness, and × if it was rough.

As is clear from Table 1, the foams of the compositions of each example had better physical properties at room temperature and high temperature than those of each comparative example, and the feel of the foam was also evaluated to be good. there were.

This is because the compositions of each Example can achieve the same foaming ratio and gel fraction as Habo with a lower dose of ionizing radiation than the compositions of Comparative Examples. Conceivable.

〔Effect of the invention〕

As detailed above, the composition for a crosslinked polypropylene foam of the present invention comprises a propylene-nonconjugated diene copolymer, optionally a propylene-ethylene random copolymer and/or a linear low-density polyethylene, and a foamed polypropylene crosslinked foam composition. It contains an agent.

Therefore, with this composition, it is possible to form a crosslinked polypropylene foam that provides a foam that has a smooth feel without substantially impairing the mechanical properties and heat resistance specific to polypropylene.

Such cross-linked foaming resin compositions utilize their surface properties, flexibility, heat resistance, and mechanical properties to be used as cushioning materials, heat insulating materials, sound deadening materials, etc. for automobile interior materials, sporting goods, food packaging, etc. Suitable for use in other exterior materials, etc.

Applicant: Tonen Petrochemical Co., Ltd.

Claims (4)

[Claims] (1) (a) a propylene-nonconjugated diene copolymer containing 0.2 to 10.0% by weight of a nonconjugated diene; (b) 1 part by weight per 100 parts by weight of the propylene copolymer;
A composition for crosslinked polypropylene foam, characterized in that it contains ~30 parts by weight of a blowing agent. (2) (a) (i) A propylene-nonconjugated diene copolymer containing 0.2 to 10.0% by weight of nonconjugated diene, and (ii) a homopolypropylene and/or ethylene content of 4% by weight or less. a propylene-ethylene random copolymer, and (b) 1 to 30 parts by weight of a blowing agent based on a total of 100 parts by weight of (i) + (ii), and (i) + (ii). ), the content of (ii) is 80% by weight or less, and the content of the non-conjugated diene is 0.2% by weight or more. Composition for use. (3) (a) (i) a propylene-nonconjugated diene copolymer containing 0.2 to 10.0% by weight of nonconjugated diene; (iii) linear low-density polyethylene; (b) the above (i) ) + 1 to 30 parts by weight of a blowing agent based on a total of 100 parts by weight of (iii) above, and 100% by weight of (i) + (iii) above.
A composition for a crosslinked polypropylene foam, characterized in that the content of the linear low density polyethylene (iii) is 50% by weight or less. (4) (a) (i) A propylene-nonconjugated diene copolymer containing 0.2 to 10.0% by weight of nonconjugated diene, and (ii) a homopolypropylene and/or ethylene content of 4% by weight or less. propylene-ethylene random copolymer; (iii) linear low-density polyethylene; (b) 1 to 30 parts by weight per 100 parts by weight of the total of (i) + (ii) + (iii). a blowing agent, the content of (ii) is 80% by weight or less, and the content of the non-conjugated diene is 0.5% by weight or less, assuming the total of (i) + (ii) as 100% by weight. 2% by weight or more, and the content of the linear low-density polyethylene (iii) is the sum of (i) + (ii) + (iii) by 1.
A composition for a crosslinked polypropylene foam, characterized in that the content is 50% by weight or less, expressed as 00% by weight.