JPH04248865A - Polyolefinic resin composition - Google Patents

Abstract

PURPOSE:To obtain a polyolefinic resin composition preventing the occurrence of die waste during extrusion molding by adding vinylidene fluoride-based rubber to a composition comprising a silane-grafted polyolefin and a silanol condensation catalyst. CONSTITUTION:A crosslinkable polyolefinic resin composition obtained by adding (C) 150-2,000ppm, preferably 250-1,000ppm vinylidene fluoride-based rubber (preferably copolymer of vinylidene fluoride and hexafluoropropylene) having 20-50, preferably 25-30 Mooney viscosity (121 deg.C) and 30,000-70,000, preferably 40,000-50,000 molecular weight by gel permeation chromatography by dissolving in tetrahydrofuran to (A) a silane-grafted polyolefin obtained by reacting a polyolefin with 0.1-50wt.% silane (preferably vinyltrimethoxysilane) in the presence of a free radical generator (preferably dicumyl peroxide) and (B) a silanol condensation catalyst (preferably dibutyltin dilaurate).

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to extruded products such as pipes for the purpose of preventing the generation of die scum that adheres to the front of the die when extruding a resin composition consisting of a silane-grafted polyolefin and a silanol condensation catalyst. The present invention relates to a polyolefin resin composition that can be crosslinked in the presence of water and is used for extrusion-coated products such as electric wires and cables.

0002

[Prior Art] Methods for crosslinking silane-grafted polyolefins are disclosed in JP-A-48-59150 and JP-A-49.
-134751, etc., and is generally known, and is widely used in the manufacturing of pipes and the field of covering electric wires and cables due to its ease of crosslinking by contacting with water in the presence of a silanol condensation catalyst. .

However, when this mixed resin of silane-grafted polyolefin and silanol condensation catalyst is molded using an extruder, die scum called "grit" is generated at the front of the die, and as time passes, the die scum accumulates and deteriorates in the product. The product deteriorates in appearance, and eventually carbonizes and adheres to the product, adversely affecting its mechanical properties and making continuous production impossible. Furthermore, the carbide adheres to the coating of electric wires or cables, not only impairing their appearance but also deteriorating their electrical insulation properties, making them unusable as electric wires or cables.

Various improvements have been attempted in the past as methods for removing die scum generated during extrusion molding. For example, methods such as burning it off using a gas burner have been used, but it is difficult to completely remove it, making continuous production difficult and posing a major problem in production. Particularly in the manufacture of products with large diameters, it is difficult to burn off die scum that accumulates at the exit of the die using a gas burner, making continuous production impossible. Therefore, although the crosslinking method is originally simple, continuous production is difficult and costs are high, so it is not necessarily economically advantageous.

[0005]

[Problems to be Solved by the Invention] The purpose is to create a significantly superior cross-linked product that can prevent the formation of die scum by adding vinylidene fluoride rubber and allows continuous production without deteriorating the appearance or properties. The present invention provides a possible polyolefin resin composition.

[0006]

[Means for Solving the Problems] The present invention is a polyolefin resin composition characterized by containing 150 to 2000 PPM of vinylidene fluoride rubber to a silane-grafted polyolefin and a silanol condensation catalyst. The rubber is a copolymer of vinylidene fluoride and propylene pentafluoride, a copolymer of vinylidene fluoride and propylene hexafluoride, or a copolymer of vinylidene fluoride and ethylene trifluorochloride, and the fluoride Vinylidene rubber is ASTM-D
Mooney viscosity at 121°C measured according to -1614 is 22-50 and soluble in tetrahydrofuran,
The polyolefin resin composition described above has a molecular weight of 30,000 to 70,000 as measured by gel permeation chromatography.

Polyolefins used in the silane-grafted polyolefin include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene-vinyl acetate copolymer.

[0008] As a method for grafting polyolefin with silane, a known method described, for example, in Japanese Patent Publication No. 1711/1983 can be employed. That is, certain polyolefins of the present invention are reacted with silane in the presence of a free radical generator, and the resulting product is then contacted with water in the presence of a silanol condensation catalyst to obtain a silane-crosslinked polyolefin.

In the present invention, the silane to be reacted with the polyolefin has the general formula SiRR'Y2 (where R is an olefinically unsaturated monovalent hydrocarbon group or a hydrocarbonoxy group, and Y is a hydrolyzable organic group). Yes, R'
is R or Y). General formula S
Examples of the group R in iRR'Y2 include a vinyl group, an allyl group, a butenyl group, a cyclohexenyl group, and a cyclopentadienyl group. Examples of the group Y include alkoxy groups such as methoxy, ethoxy, and butoxy groups, alkyloxy groups such as formyloxy, acetoxy, and propionoxy groups, oxime groups, alkylamino groups, and arylamino groups. The most preferred examples of these silanes include vinyltrimethoxysilane and vinyltriethoxysilane. The proportion of silane used can be changed arbitrarily depending on the reaction conditions or the degree of modification, but it is generally 0.00% relative to the polyolefin to be modified.
It is 1 to 50% by weight, preferably 0.5 to 10% by weight.

[0010] As the free radical generator, organic peroxides and peresters are preferred. Specific examples of these are:
Benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide,
2,5-di(peroxybenzoate)hexyne-3,
1,3-bis(tert-3-butyl-peroxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-dimethyl-(tert-butylperoxy)hexyne- Mention may be made of 3,2,5-dimethyl-2,5di(tert-butylperoxy)hexane and tert-butylperbenzoate, azo compounds such as azobisisobutyronitrile and dimethylazodiisobutyrate; Mil peroxide is most preferred.

[0011] As a method for silane-modifying a polyolefin, the polyolefin, silane, and a free radical generator are mixed and reacted in any suitable apparatus. Reaction temperature is 100℃
It is carried out at any temperature above and below the decomposition temperature of the polyolefin, preferably at 120 to 250°C. The reaction time is preferably up to 10 minutes, preferably 2 to 5 minutes. Further, as the reaction device, any device can be used, such as an extruder, a Banbury mixer, a roll mill, or the like.

[0012] A known method can be used to crosslink the obtained silane-modified polyolefin. That is, after a silane-modified polyolefin is molded using an extruder or other processing, it is brought into contact with water in the presence of a silanol condensation catalyst to cause a reaction, thereby obtaining a crosslinked polyolefin.

Silanol condensation catalysts include, for example, dibutyltin dilaurate, stannous acetate, stannous octoate (stannous caprylate), lead naphthenate, zinc caprylate, iron 2-ethylhexanoate, and cobalt naphthenate. Organic bases such as ethylamine, hexylamine, di- Mention may be made of butylamine and pyridine, acids such as inorganic acids and fatty acids. Suitable catalysts are organotin compounds such as dibutyltin dilaurate, dibutyltin diacetate and dibutyltin dioctoate.

The silanol condensation catalyst is preferably mixed into the silane-modified polyolefin before contacting with water. That is, this can be achieved by mixing a silanol condensation catalyst before, during, or after the reaction between the silane and the polyolefin. The amount of silanol condensation catalyst added is 0.01 to 0.5% by weight based on the unmodified polyolefin.
The content is particularly preferably 0.02 to 0.2% by weight.

Examples of the vinylidene fluoride rubber include a copolymer of vinylidene fluoride and propylene pentafluoride, a copolymer of vinylidene fluoride and propylene hexafluoride, or a copolymer of vinylidene fluoride and ethylene trifluorochloride. Copolymers may be mentioned, and in the present invention, a copolymer of vinylidene fluoride and propylene hexafluoride is particularly suitable. The amount of vinylidene fluoride rubber added is 150 to 2000 PPM, especially 250 to 2000 PPM.
1000 PPM is preferred. If the amount of vinylidene fluoride rubber added is less than 150 PPM, the lubricity will be insufficient and it will not be effective in preventing die scum, and even if it is added more than 2000 PPM, the effect will reach saturation, and on the contrary, the electrical properties will deteriorate, which is a bad result. cannot be obtained. Also, vinylidene fluoride rubber has AS
The Mooney viscosity at 121°C measured according to TM-D-1614 is 20 to 50, and the molecular weight measured by gel permeation chromatography is 30,000 to 70,000 when dissolved in tetrahydrofuran. If the molecular weight is less than 30,000 or less, the lubricity will be insufficient, and if the Mooney viscosity is 50 or more or the molecular weight is 70,000 or more, the compatibility with vinylidene fluoride rubber will be poor. Particularly preferred are Mooney viscosity of 25 to 30 and molecular weight of 40,000 to 5.
It belongs to ten thousand people.

The mechanism of generation of die scum is that when the mixture of silane-grafted polyolefin and silanol condensation catalyst is extruded, crosslinking gradually progresses in the extruder, and the flow of the resin on the inner wall of the machine is slowed down, causing the crosslinked product to adhere to the inner wall of the machine. It is thought that the so-called resin crosslinked material is generated as die scum, which accumulates, becomes extruded as die scum together with the extruded product, and accumulates in front of the die outlet. Although this phenomenon cannot be left out of the realm of speculation, when the resin passes through the extruder and die,
It is thought that a thin film of the added vinylidene fluoride rubber is formed on the metal surface, and the surface of the film is highly slippery, which prevents the resin from stagnation and the generation of so-called die scum.

[0017] Generally, plastic compositions have a very high affinity for metals, and decomposed products and crosslinked products generated within the extruder or on the inner wall of the die where they tend to accumulate tend to form die scum. However, a coating of vinylidene fluoride rubber with high surface smoothness is formed on the metal surface, which reduces its affinity with the metal and improves the fluidity of the resin, allowing it to pass through the die without staying inside the die. It is thought that this can be prevented from occurring.

Vinylidene fluoride rubber may be added during the production of a masterbatch of a silanol condensation catalyst, or it may be added during the production of a silane-grafted polyolefin obtained by grafting a hydrolyzable organic silane compound onto a polyolefin. Alternatively, a masterbatch of vinylidene fluoride rubber or vinylidene fluoride rubber may be added when mixing the silane-grafted polyolefin and the silanol condensation catalyst.

In the present invention, additives such as pigments, antioxidants, ultraviolet absorbers, flame retardants, and inorganic fillers may be added to facilitate identification depending on the purpose.

[0020]

[Example] (Production of masterbatch of silanol condensation catalyst) Low density polyethylene (PE) with a density of 0.922 and a melt flow of 1.5 was used as the base resin.
To 100 parts by weight, 1 part by weight of dibutyltin dilaurate (manufactured by Sankyoki) as a silanol condensation catalyst and various additives were mixed in a mixer, and some of the following 10 types (CM1 to CM10) were mixed. produced a masterbatch of silanol condensation catalyst containing a high concentration of vinylidene fluoride rubber. CM1: No other additives CM2: Stearic acid
2 parts by weight CM3: Polyethylene wax
10 parts by weight CM4: silicone wax
20 parts by weight CM5: silicone oil
20 parts by weight CM6: Vinylidene fluoride rubber
0.2 parts by weight CM7: Vinylidene fluoride rubber
5 parts by weight CM8: Vinylidene fluoride rubber
0.4 parts by weight CM9: Vinylidene fluoride rubber
2 parts by weight CM10: Vinylidene fluoride rubber 3 parts by weight The vinylidene fluoride rubber used is a copolymer of vinylidene fluoride and propylene hexafluoride with a molecular weight of 45,000 and a Mooney viscosity of 28.

(Manufacture of silane-grafted polyolefin) Low density polyethylene (PE) with a density of 0.922 and a melt flow of 1.5 is used as the polyolefin.
To 100 parts by weight, 3 parts by weight of vinyltrimethoxysilane and 0.3 parts by weight of dicumyl peroxide are mixed and kneaded in an extruder to produce silane-grafted polyethylene (hereinafter referred to as S
0-1) was produced. Add 0.1 part by weight of the vinylidene fluoride rubber, which is a copolymer of vinylidene fluoride and propylene hexafluoride, with a molecular weight of 45,000 and a Mooney viscosity of 28, to the same formulation as SO-1, and use the same method. Silane-grafted polyethylene (hereinafter SO
-2) was produced.

<<Comparative Examples 1 to 7, Examples 1 to 3>> Using SO-1 as the silane grafted polyolefin,
To 95 parts by weight of O-1, 5 parts by weight each of CM1 to CM10 were added as silanol condensation catalysts, mixed in a mixer, extrusion molded under the following conditions, and evaluated by the amount of die scum attached to the front of the die. did. The results are shown in Table 1 along with other evaluation results. Extruder: 50mmφE×t, L/D=22, CR=3.
5 Die: 12mmφ tube die: chrome plating inside of mouth Temperature: C1: 120℃, C2: 160℃, C3: 1
70°C, C4: 180°C, D1: 170°C, D2: 170°C Discharge rate: 40 rpm, 15 kg/hr The examples in which the amount of vinylidene fluoride rubber added was 150 to 2000 PPM were good in all evaluation items. On the other hand, in Comparative Example 6 in which the amount of vinylidene fluoride rubber added was 150 PPM or less, and in other comparative examples in which no vinylidene fluoride rubber was added, a large amount of die scum was generated and the effect was poor, and the amount of vinylidene fluoride rubber added was 2000 PPM. In Comparative Example 7, no die scum was generated, but the electrical properties deteriorated, which is not preferable.

<<Example 4>> Using SO-2 as the silane-grafted polyolefin, 5 parts by weight of CM1 as a silanol condensation catalyst was mixed with 95 parts by weight of the SO-2, and evaluation was performed in the same manner as above. The results are shown in Table 1. Good results were obtained with no occurrence of die scum.

<<Example 5>> SO-1 was used as the silane-grafted polyolefin, and 5 parts by weight of CM1 as a silanol condensation catalyst and the same vinylidene fluoride as used above were added to 95 parts by weight of the SO-1. Series rubber 0
．． 1 part by weight was mixed and evaluated in the same manner as above, and the results are shown in Table 1. Good results were obtained with no occurrence of die scum.

C of masterbatch of silanol condensation catalyst
Using the same materials as M8, 2 parts by weight of vinylidene fluoride rubber were mixed with 100 parts by weight of the PE in a mixer, and then kneaded and granulated in a Banbury mixer to produce a masterbatch of vinylidene fluoride rubber. Using SO-1 as the silane-grafted polyolefin, 5 parts by weight of CM1 as a silanol condensation catalyst and 5 parts by weight of the vinylidene fluoride rubber masterbatch prepared above are mixed with 95 parts by weight of the SO-1, Evaluation was performed in the same manner as above, and the results are shown in Table 1. Good results were obtained with no occurrence of die scum.

[0026]

[Table 1]

[0027]

Effects of the Invention The present invention is a crosslinkable polyolefin resin composition that does not require special equipment or special methods to remove die scum generated during extrusion molding, and can prevent the generation of die scum and has good electrical properties. It is a highly economical invention that has good productivity and excellent continuous productivity, resulting in significant cost reductions and process rationalization.

Claims (3)

[Claims] Claim 1: 15% vinylidene fluoride rubber to silane-grafted polyolefin and silanol condensation catalyst.
A polyolefin resin composition characterized by containing 0 to 2000 PPM. 2. The vinylidene fluoride rubber is a copolymer of vinylidene fluoride and propylene pentafluoride, a copolymer of vinylidene fluoride and propylene hexafluoride, or a copolymer of vinylidene fluoride and propylene hexafluoride.
The polyolefin resin composition according to claim 1, which is fluorochlorinated ethylene. [Claim 3] Vinylidene fluoride rubber meets ASTM-D
Mooney viscosity at 121°C measured according to -1614 is 20-50 and soluble in tetrahydrofuran,
The polyolefin resin composition according to claim 1, which has a molecular weight of 30,000 to 70,000 as measured by gel permeation chromatography.