JPS62141035A - Production of crosslinked insulating material - Google Patents

Abstract

PURPOSE:To obtain the titled material without using any peroxide at a low temperature in a one-stage process, by exposing a graft copolymer obtained from an alkylene/alkyl acrylate copolymer and a specified alkoxysilane. CONSTITUTION:A graft polymer obtained by effecting ester exchange and graft addition of 100pts.wt. alkylene/alkyl acrylate copolymer (A) (e.g., ethylene/ethyl acrylate copolymer of a methyl methacrylate content of 5-50wt% and 0.2-15.0 pts.wt. alkoxysilane (B) having a carboxyl group, an amino group or a mercapto group as a functional group (e.g., gamma-methacryloxypropyltrimethoxysilane) at 180 deg.C or below in an extruder in the presence of 0.1-8.0pts.wt. organoaluminum catalyst [e.g., aluminum(ethylatoaluminum dibenzoate)monoisopropylate] is exposed to water in the presence of a silanol condensation catalyst (e.g., dibutyltin dilaurate) to form crosslinkages between the functional groups.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for producing a crosslinked insulating material, and particularly relates to a one-step silane crosslinking process in which a graft addition reaction and extrusion are performed in the same step. This relates to a manufacturing method that allows a silane graft reaction and extrusion molding to be performed at low temperatures by performing transesterification without using peroxide as an initiator during the reaction, thereby producing a crosslinked insulating material. be.

(Prior Art) A method for crosslinking polyolefins with a silane compound is already known from Japanese Patent Publication No. 1711/1983. In this crosslinking method, an initiator such as a peroxide is applied to polyolefins to generate radicals, and an alkoxysilane having a reactive group such as a vinyl group is grafted onto the polyolefin. This is a two-step process in which the graft polymer is then exposed to a moisture atmosphere in the presence of a silanol condensation catalyst to carry out silanol condensation. However, this two-stage process method has the disadvantage that it requires one more step, and that when the graft polymer is stored for a long time, silanol condensation occurs due to the moisture contained in the raw material polyolefin and silane.

As a method to improve this problem, a one-step process method has been proposed in which polyolefins, alkoxysilanes, and per[monide silanol condensation catalysts] are simultaneously blended and these are extruded at once.

This one-step process method is advantageous in terms of both cost and production, since the steps are short and there is no problem with the storage stability of raw materials.

(Problems with the Prior Art) In the one-step process described above, if a high-temperature decomposition type peroxide such as dicumyl peroxide is used as a graft initiator, the temperature must be raised to a high temperature of about 180° C. to 200° C. Therefore, for example, when covering a conductor with cloth wrapped around it, interfacial foaming occurs between the cloth and the crosslinked insulating material.

In addition, when fillers and additives containing hydrates are added to the silane graft polymer obtained by the conventional method, the water contained in the hydrates decomposes and reacts with the silane graft polymer, resulting in scorch and foaming. etc. will occur. Therefore, in these cases, it is necessary to carry out extrusion processing at a low temperature. However, since dicumyl peroxide is a high-temperature decomposition type peroxide, it does not provide a sufficient degree of crosslinking when used at low temperatures. In addition, when low-temperature decomposition type peroxides such as benzoyl permoxide are used, the effect of contributing to crosslinking is small, so the degree of crosslinking obtained is small, and the storage stability of the peroxide itself is poor. However, there were problems such as the effective amount changing over time and the optimum amount to be added being unknown.

OBJECTS OF THE INVENTION It is an object of the present invention to perform silane crosslinking at low temperatures and in a one-step process by avoiding the use of peroxides used as grafting initiators.

(Structure of the Invention) An alkoxysilane having a carboxyl group, an amino group, or a mercapto group as a functional group is added to an alkylene/alkyl acrylate copolymer in the presence of an organoaluminum catalyst, and the alkylene/alkyl acrylate copolymer and the alkoxysilane are It is characterized by grafting an alkoxysilane group through transesterification and exposing the resulting graft polymer to a moisture atmosphere in the presence of a silanol condensation catalyst to carry out a silanol condensation reaction and generate crosslinks between functional groups. It is something to do.
:2. ．．
1゜fulkylene-fulkylacrylate copolymer and
:■′,.

and ethylene/ethyl acrylate copolymer,
□゛゛゛Ethylene thyl acrylate° copolymer is preferred. The ethyl acrylate content in the ethylene ethyl acrylate copolymer and the methyl acrylate content in the ethylene methyl acrylate copolymer can range from 5 to 50% by weight, but preferably from 10 to 30% by weight.

The functional group of alkoxysilane that binds to the alkylene/alkyl acrylate copolymer is represented by can be expressed as

H-C-H 1l-C-14 (R, R': alkyl group) Or -NH2.

As the alkoxysilane, γ-methacryloxypropyltrimethoxysilane, T-mercaptopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane can be used, but γ-methacryloxypropyltrimethoxysilane is preferred. . The amount of alkoxysilane added is 10% of the alkylene alkyl acrylate copolymer.
With respect to 0 parts by weight, 0.2 to 15.0 parts by weight are possible, and 1.0 to 10.0 parts by weight are suitable.

As the organoaluminum catalyst, aluminum isopropylate, aluminum ethylate, and aluminum dibenzoate monoisopropylate can be used, but in descending order of degree of crosslinking, aluminum dibenzoate monoisopropylate, aluminum isopropylate, and aluminum ethyl It becomes lat. The amount of the organoaluminium-based catalyst added can be 0.1 to 8.0 parts by weight, preferably 0.2 to 5.0 parts by weight, based on 100 parts by weight of the alkylene alkyl acrylate copolymer.

As the silanol condensation catalyst, any catalyst known in Japanese Patent Publication No. 1711/1984 may be used, and suitable examples include dibutyltin dilaurate, dibutyltin diacetate, and diptyltin dioctoate.

In addition to these, anti-aging agents, antistatic agents, flame retardants, pigments, fillers, etc. can be added as necessary.

In particular, it was impossible to add hydrate-based flame retardants using the conventional one-step process method that uses high-temperature decomposition type peroxides because foaming and scorch occur due to the silanol condensation reaction. With this method, it is now possible to add it by performing extrusion processing at a lower temperature than before.

The method for producing the crosslinked insulating material of the present invention includes (A) an alkylene alkyl acrylate copolymer, (B) an alkoxysilane, (C) an organoaluminum catalyst, (D) a silanol condensation catalyst, and (E) as necessary. Five types of additives such as fillers and flame retardants, or (A) to (D)
An example of this method is heating and kneading the surrounding area. In this case, the above five components or (A) to (D) may be heated and kneaded at the same time, or (A) and (D) may be premixed in advance, and then the remaining components may be added and heat kneaded. There are methods etc.

As the heating kneading device, commonly used kneading machines such as various types of extruders, Braenders, Banbury mixers, kneaders, mixing rolls, etc. can be used. When using the one-stage process method, it is preferable to use an extruder that has been devised to improve kneading properties, such as an 8M screw manufactured by Swiss company Myfer or a Madtsuk type screw manufactured by American Davis Standard. Good to use. Further, in order to ensure sufficient reaction time, L/D is preferably large, preferably 30 or more, and it is also preferable that the pitch interval, which is usually the diameter of the screw, be smaller than D.

Regarding the heating kneading temperature, the present invention has the feature that extrusion processing can be performed at a lower temperature than before, and the heating kneading temperature is 140~
180°C is possible, but 150-170°C is preferred.

The method of the present invention will be explained below with reference to Examples. "Part" in the main text
represents "parts by weight".

Comparative Example 1 100 parts of ethylene ethyl acrylate copolymer (ethyl acrylate content: 18% by weight) and 0.05 part of dibutyltin dilaurate were thoroughly mixed with a mixing roll and pelletized to obtain pellets.

The pellets dried at 70°C for 112 hours are referred to as component A. 00 parts of component Al, 3.0 parts of vinyltrimethoxysilane, and 0.15 parts of dicumyl peroxide were thoroughly mixed in a Henschel mixer to obtain a mafushi mixture. This mixture was supplied to an extruder having a full-flight screw with L/D・30, D=55 mmφ, pitch number 50, and compression ratio 3.2.
It was coated on a 0.9 mm diameter conductor wrapped with cloth at 0°C and immersed in water at 80°C for 24 hours.

The results are shown in Table-1.

Comparative Example 2 A wire covering was obtained in the same manner as Comparative Example 1 except that extrusion was carried out at a temperature of 160°C instead of 190°C. The results are shown in Table-1.

Comparative Example 3 0.15 parts of benzoyl peroxide was used instead of 0.15 parts of dicumyl peroxide, and the extrusion temperature was 160.
A wire covering was obtained in the same manner as in Comparative Example 1 except that the temperature was changed to .degree. The results are shown in Table-1.

Example 1 4.0 parts of γ-methacryloxypropyltrimethoxysilane was used instead of 3.0 parts of vinyltrimethoxysilane, and 1 part of aluminum isopropylate was used instead of 0.15 parts of dicumyl peroxide. Using .0 parts,
A wire coating was obtained in the same manner as in Comparative Example 1 except that the extrusion temperature was 160°C. The results are shown in Table 1.

Example 2 Example 1 except that 1.0 part of aluminum ethylate was used instead of 1.0 part of aluminum isopropylate.
A wire covering was obtained in the same manner as in . The results are shown in Table-1.

Example 3 1.0 part of aluminum dibenzoate monoisopropylate instead of 1.0 part of aluminum isopropylate
A wire covering was obtained in the same manner as in Example 1 except that the wire coating was used. The results are shown in Table-1.

Comparative Example 4 100 parts of ethylene ethyl acrylate copolymer (ethyl acrylate content 18%), 10 parts of aluminum hydroxide
0 parts, butyltin dilaure) 0.05 parts, red phosphorus 2
, 0 parts, low molecular weight ethylene propylene rubber 0.3 parts,
Pentaerythrityl-tetrakis [3-(3,5-di-
t-Butyl-4-hydroxyphenyl)propione-h
) 1.0 parts, silicone rubber (CF9150, trade name manufactured by Toray Silicone Co., Ltd.) 2.0 parts, carbon black 1.0 parts.
0 parts were thoroughly mixed with a mixing roll and pelletized to obtain pellets. This pellet was dried at 70°C for 112 hours and is referred to as component B. This component B is 206.4
1 part, 3.0 parts of vinyltrimethoxysilane, and 0.15 parts of dicumyl peroxide were thoroughly mixed in a Henschel mixer to obtain a mixture. This mixture is L/D
=30, D=55, φ, pitch number 50, compression ratio 3.2
The mixture was supplied to an extruder having a full-flight screw, and sheet extrusion was performed at a rotation speed of 10 r, p, m, and a temperature of 190°C.

The results are shown in Table-2.

Comparative Example 5 A sheet was obtained in the same manner as Comparative Example 4, except that extrusion was performed at a temperature of 160°C instead of 190°C.

The results are shown in Table-2.

Comparative Example 6 0.15 parts of benzoyl peroxide was used instead of 0.15 parts of dicumyl peroxide, and the extrusion temperature was set at 160°C.
A sheet was obtained in the same manner as in Comparative Example 4 except that the temperature was changed to °C. The results are shown in Table-2.

Instead of 3.0 parts of vinyltrimethoxysilane, 4.0 parts of γ-methacryloxypropyltrimethoxysilane was used, and 1 part of aluminum isopropylate was used instead of 0.15 parts of dicumyl peroxide. A sheet was obtained in the same manner as in Comparative Example 4, except that .0 part was used and the extrusion temperature was 160°C. The results are shown in Table-2.

Example 5 A sheet was obtained in the same manner as in Example 4, except that 1.0 part of aluminum ethylate was used instead of 1.0 part of aluminum isopropylate. The results are shown in Table-2.

Example 6 1.0 part of aluminum dibenzoate monoisopropyrate was substituted for 1.0 part of aluminum isopropylate.
A sheet was obtained in the same manner as in Example 4 except that

The results are shown in Table-2.

This 1 m-1 Component B is referred to as Component C, in which 50 parts of magnesium hydroxide is used instead of 100 parts of aluminum hydroxide. Instead of 8206.4 parts of component, 56.4 parts of component Cl.
A sheet was obtained in the same manner as in Comparative Example 4 except that 4 parts were used. The results are shown in Table-2.

Table 1 Table 2 KotJushi-1 A sheet was obtained in the same manner as Comparative Example 5.6 except that 156.4 parts of component C was used instead of 206.4 parts of component B. The results are shown in Table-2.

Examples 7 to 9 Sheets were obtained in the same manner as Examples 4 to 6, except that 156.4 parts of component C was used instead of 206.4 parts of component B. The results are shown in Table-2.

(Effect of the invention) As is clear from the results in Tables 1 and 2, dicumyl peroxide, which is a high-temperature decomposition type peroxide, was heated at a high temperature of 190°C as in Comparative Examples 1 and 4.7. When used, there is no problem with the degree of crosslinking, but in Comparative Example 1, interfacial foaming occurred between the cloth and the crosslinked insulating material, and in Comparative Example 4.
．． In No. 7, foaming occurred within the crosslinked insulating material, resulting in an unfavorable appearance. Also, Comparative Examples 2, 5.
8, when dicumyl peroxide, which is a high-temperature decomposition type peroxide, is used at a low temperature of 160°C, and as shown in Comparative Examples 3 and 6.9, when dicumyl peroxide, which is a low-temperature decomposition type peroxide, is used, When the oxide was used at 160°C, there were no problems with appearance and foaming, but the degree of crosslinking was too small.

On the other hand, as in Examples 1 to 9, when an organoaluminum catalyst was used instead of peroxide, 16
Good results were shown in terms of appearance, foaming, and degree of crosslinking at a low temperature of 0°C.

The method of the present invention allows extrusion processing at lower temperatures than conventional methods, and therefore, in cases where high temperatures would be disadvantageous, for example, one-step processes such as systems that incorporate fillers and additives containing hydrates, etc. This is a particularly effective method.

Procedural amendment September 2, 1988 Commissioner of the Patent Office Black 1) Akio Yu 1, Indication of the case 1985 Patent Application No. 279277 2, Name of the invention Process for manufacturing cross-linked insulating material 3, Person making the amendment Case Relationship with Patent applicant (529) Furukawa Electric Co., Ltd. 4, Agent 6, Subject of amendment\□ 1. The text between page 1, line 3, and page 2, line 12 of the specification is corrected as follows.

``2. Claim 1: In the alkylene/alkyl acrylate copolymer,
Graft addition is performed by transesterifying an alkoxysilane having a carboxyl group, an amino group, or a mercapto group as a functional group in the presence of an organoaluminum catalyst, and the resulting graft polymer is exposed to moisture in the presence of a silanol condensation catalyst. A method for producing a crosslinked insulating material, characterized in that crosslinking is produced between functional groups.

2. The method according to claim 1, characterized in that the graft reaction is carried out at a material temperature of 180°C or less using an extruder as a reaction vessel during the graft reaction, and extrusion molding is also carried out at the same time. A method for producing a crosslinked insulating material.

3. The method for producing a crosslinked insulating material according to claim 1, wherein the alkylene/alkyl acrylate copolymer is an ethylene/ethyl acrylate copolymer or an ethylene/methyl acrylate copolymer.

4. The method for producing a crosslinked insulating material according to claim 1, wherein the alkoxysilane is γ-methacryloxypropyltrimethoxysilane.

5. Claim 1, wherein the organoaluminium-based catalyst is any compound selected from the group of aluminum isopropylate, aluminum ethylate, aluminum dibenzoate monoisopropylate.
A method for producing a crosslinked insulating material as described in Section 1. 2. On page 3 of the specification, line 18, "Peroxide, silanol condensation" is corrected to "Peroxide, silanol condensation."

3. On page 4, line 19, "penzoyl permiki" is corrected to "benzoyl permiki."

4. Line 11 from just below No. 7 I am corrected.

5. On page 9, line 15, "Various extruders, Brabender" is corrected to "Various extruders, Brabender."

6. On page 9, line 19, ``Mipha Co., Ltd.'' is corrected to ``Mipha Co., Ltd.''.

7. On page 10, line 20, and on page 13, line 8, "Henschel mixer" is corrected to "Henschel mixer."

8. On page 11, line 19, "dicumyl peroxide" is corrected to "dicumyl peroxide."

9. On page 12, line 2, "Wire coating was obtained." is corrected to "Wire coating was obtained."

10. On page 12, line 17, "butyltin dilaurate" is corrected to "diptyltin dilaurate."

11, page 12, line 20 “-4-hydroxypheny”
is corrected to "-4-hydroxypheny".

12. On page 13, line 9, ``Mazushi mixture'' is corrected to ``Mabushi mixture''.

Claims (1)

[Claims] 1. Graft addition of an alkoxysilane having a carboxyl group, an amino group, or a mercapto group as a functional group to an alkylene/alkyl acrylate copolymer by transesterification in the presence of an organoaluminum catalyst; 1. A method for producing a crosslinked insulating material, which comprises exposing the obtained graft polymer to moisture in the presence of a silanol condensation catalyst to generate crosslinks between functional groups. 2. Using an extruder as a reaction vessel during the graft reaction 1
2. The method for producing a crosslinked insulating material according to claim 1, wherein the graft reaction is carried out at a material temperature of 80° C. or lower, and extrusion molding is also carried out at the same time. 3. The method for producing a crosslinked insulating material according to claim 1, wherein the alkylene/alkyl acrylate copolymer is an ethylene/ethyl acrylate copolymer or an ethylene/methyl acrylate copolymer. 4. The method for producing a crosslinked insulating material according to claim 1, wherein the alkoxysilane is γ-methacryloxypropyltrimethoxysilane. 5. The crosslinked insulation according to claim 1, wherein the organoaluminium-based catalyst is any compound selected from the group of aluminum isopropylate, aluminum ethylate, and aluminum dibenzoate monoisopropylate. Method of manufacturing the material.