JP3322818B2 - Method for producing silane-crosslinked polyolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a silane crosslinking agent masterbatch impregnated with a high concentration of an organic unsaturated silane in the silane crosslinking of polyolefin, and a catalyst masterbatch containing the same and a silanol condensation catalyst. The present invention relates to a silane crosslinking method for producing a silane-crosslinked polyolefin in one step.

[0002]

2. Description of the Related Art Conventionally, as a simple method of crosslinking a polyolefin, a polysilane is graft-reacted with an organic unsaturated silane in the presence of a free radical generator, followed by silane grafting. A so-called silane cross-linking method of cross-linking by contacting with moisture in the presence of is generally known. For example, Tokiko 48
-1711, JP-A-57-49109 and the like.

[0003] However, this method involves at least two steps. That is, a silane grafting reaction step and a silanol condensation reaction step. Therefore, at least two extrusion steps are required, and an economic problem as an end product cannot be avoided. As a one-step process, there is a mono-seal method. However, this method requires a liquid addition device for injecting the organic unsaturated silane in a liquid state into the extruder, but has problems of slippage and poor measurement. In addition, an extruder requires an expensive and special type having a large L / D in order to uniformly disperse a small amount of additives, and an economical problem cannot be avoided. In addition, very high technology is required for extrusion.

Further, as a one-step process, a silane crosslinking method in which silane is introduced into a solid carrier polymer is disclosed in JP-A-3-167229. In this method, the solid carrier polymer includes a porous polymer, a swellable polymer, and a capsule. Preferred materials for the porous polymer are ethylene-vinyl acetate copolymer (hereinafter referred to as EVA), high-density polyethylene, low-density polyethylene, And linear low-density polyethylene.

However, these porous polymers require a process for making them porous, and have problems of productivity and economy. Also, EV is a preferable material of the swellable polymer.
A is cited, but EVA has problems such as insufficient silane impregnation, poor thermal stability, and the risk of copper damage due to decomposition product acetic acid and poor electrical properties.

A silane crosslinking method in which silane is introduced into a foamed resin is disclosed in Japanese Patent Application Laid-Open No. Hei 7-330914. In this method, a foamed resin of an ethylene copolymer in which the silane crosslinking agent holder has a carbonyl group-containing comonomer content of 30% by weight or more is mentioned. However, this also requires a foaming step, and the problems of productivity and economy are inevitable. In this publication, the method of impregnating the foamed resin with the silane crosslinking agent liquid is performed by rotating and mixing in a closed container at room temperature for one hour, which takes a considerable amount of time and causes a problem in productivity. Further, in the above two publications, additives such as a silanol condensation catalyst and an antioxidant are introduced into the solid polymer in addition to the silane and the free radical generator. For this reason, there is a major problem that crosslinking efficiency and storage stability are poor due to oligomerization by condensation of silane or crosslinking inhibition by radical scavenging.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve these problems and is an efficient method for producing a silane crosslinking agent masterbatch impregnated with a high concentration of an organic unsaturated silane in silane crosslinking of a polyolefin. Another object of the present invention is to provide a silane cross-linking method for producing a silane cross-linked polyolefin excellent in cross-linking efficiency in one step by using the silane cross-linking agent master batch and a catalyst master batch containing a silanol condensation catalyst and the like.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made to find a carrier polymer capable of impregnating an organic unsaturated silane or the like at a high concentration and a method for easily producing a silane crosslinking master batch by examining the impregnation conditions at that time. And a method for producing a silane-crosslinked polyolefin having excellent crosslinking efficiency by employing a catalyst masterbatch further containing a silanol condensation catalyst and the like.

That is, the present invention relates to a carrier comprising an ethylene-unsaturated ester copolymer comprising (i) a polyolefin-based base polymer and (ii) a silane crosslinking agent which is a liquid organic unsaturated silane containing a free radical generator. A polymer, a silane crosslinker masterbatch impregnated at a temperature close to or lower than the melting point of the carrier polymer, and (iii) a catalyst masterbatch containing a silanol condensation catalyst and an antioxidant, from the crystal melting point of all polymers. A method for producing a silane-crosslinked polyolefin in which the components are melt-mixed and reacted at a high temperature, and then contacted with water to crosslink the silane-crosslinked polyolefin. More preferably, the comonomer content of the ethylene-unsaturated ester copolymer is 18 to 41% by weight. Yes, the amount of the organic unsaturated silane added is 10 to the carrier polymer.
40% by weight, and the ethylene-unsaturated ester copolymer is an ethylene-ethyl acrylate copolymer,
A methyl methacrylate copolymer or a mixture thereof, the organic unsaturated silane is vinyltrimethoxysilane or vinyltriethoxysilane, and the free radical generator is dicumyl peroxide or α, α ′.
-Bis (t-butylperoxydiisopropyl) benzene, and the carrier polymer was previously 5
After preheating to a temperature lower by ３０30 ° C., the silane crosslinking agent is charged while stirring into a closed mixer maintained at a temperature lower by 5 to 30 ° C. than the melting point, and the mixture is sealed. The carrier polymer is impregnated with a silane crosslinking agent under a pressure of 0.1 to 10 kg / cm ² under nitrogen pressure, and the carrier polymer of the catalyst master batch has a melting point of a polyolefin-based base polymer. A method for producing a silane-crosslinked polyolefin comprising polyethylene, polypropylene, a copolymer of ethylene and an α-olefin having a melting point higher than that of the above, and a total amount of the silane crosslinker masterbatch and the catalyst masterbatch of 3 to 15% by weight. It is.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The polyolefin-based base polymer of the present invention is not particularly limited, but is a general polyethylene, polypropylene, a copolymer of ethylene and an α-olefin, and the α-olefin is C _{3 to} C ₁₂ such as propylene, Butene-1, pentene-1, octene-1, 4-
Methylpentene-1,4-methylhexene-1,4,4
-Dimethylpentene-1, nonene-1, decene-1, undecene-1, dodecene-1 and the like. Or EE
A, EMMA, EVA, chlorinated polyethylene (CP
E) and mixtures thereof.

The organic unsaturated silane of the present invention is one which is grafted to the base resin so as to be a cross-linking point between the base resins. The organic unsaturated silane used in the present invention is represented by the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R 'is an aliphatic unsaturated hydrocarbon group. Monovalent hydrocarbon groups other than hydrogen or
The same compound as used for Y) is used. It is desirable to use an organic unsaturated silane represented by the general formula RSiY _{3 in} which R ′ is the same as Y, for example, vinyltrimethoxysilane,
Vinyl triethoxy silane, vinyl tributoxy silane, allyl trimethoxy silane, allyl triethoxy silane and the like can be mentioned.

The amount of the silane to be added is 10 to 40% by weight, preferably 20 to 3% by weight based on the total weight of the carrier polymer in the silane crosslinking agent masterbatch.
0% by weight. If the amount is less than 10% by weight, sufficient grafting does not occur. If the amount is more than 40% by weight, bleeding of silane occurs when a load is applied to the impregnated pellets. In the silane-crosslinked polyolefin, the silane content is 0.1 to 5% by weight, preferably 0.7 to 3% by weight based on the total weight of the polymer. 0.1% by weight
If less than 5%, sufficient grafting does not occur, and 5% by weight
If the ratio exceeds the above range, molding failure will occur and it will not be economical.

[0013] The free radical generator of the present invention acts as an initiator of the silane grafting reaction. The free radical generator used in the present invention includes various organic peroxides and peresters having a strong polymerization initiating action, such as dicumyl peroxide, α, α'-bis (t-butylperoxydiisopropyl) benzene, Di-t-butyl peroxide, t-butyl cumyl peroxide, di-benzoyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylperoxypivalate, t -Butylperoxy-2-ethylhexanoate and the like. These are added in an amount of 0.01 to 0.5% by weight, preferably 0.05 to 0.5% by weight, based on the total weight of the polymer in the silane-crosslinked polyolefin.
0.2% by weight. When the amount is less than 0.01% by weight, a sufficient silane grafting reaction does not proceed. When the amount exceeds 0.5% by weight, the extrudability decreases and the molding surface deteriorates.

The silane crosslinker masterbatch of the present invention comprises:
By swelling the carrier polymer with a liquid mixture of a free radical generator dissolved in an organic unsaturated silane,
It can be prepared by impregnating a carrier polymer with a free radical generator and an organic unsaturated silane. At this time, in order to efficiently impregnate the organic unsaturated silane at a high concentration in a short period of time, the carrier polymer must be preliminarily melted at a temperature of 5 to 5
It is preheated to a temperature lower by 30 ° C., put into a closed mixer kept at a temperature 5 to 30 ° C. lower than its melting point, and the liquid mixture is charged with stirring. After the charging, the mixer is sealed and pressurized. It is necessary to carry out mixing and impregnation, and it is preferable to carry out the reaction under nitrogen pressure in order to prevent the influence of moisture in the air.
The temperature must be lower than the melting point of the carrier polymer so that the carrier polymer does not melt.However, if the temperature is too close to the melting point, there is a risk of blocking the polymer and adhering to the mixer. Not preferred. At a temperature lower than the melting point by 30 ° C. or more, there is a problem that the liquid mixture is not impregnated or it takes a long time for impregnation, which is not preferable.

As a mixer for impregnating the organic unsaturated silane at a high temperature, a closed type mixer is preferable in order to prevent volatilization of the organic unsaturated silane. Nitrogen pressurization is also preferred for efficient impregnation in a short time and minimizing the possibility of early hydrolysis and condensation of the organic unsaturated silane. The pressure is preferably 0.1 to 10 kg / cm ² . 0.1kg / c
If it is less than m ² , efficient impregnation cannot be obtained and 10 kg /
If it exceeds cm ² , the cost will increase as equipment specifications. Suitable mixers include Dalton mixers, supermixer mixers, tumbler mixers and the like.

The carrier polymer must be in particulate form and be solid compatible with the crosslinkable base polymer and the organic unsaturated silane. Compatible means that the carrier polymer must not readily react with the organic unsaturated silane and must be dispersible or soluble in the base polymer. Suitable carrier polymers are non-hygroscopic. That is, it is preferred that water absorption be relatively slow to minimize the potential for premature hydrolysis and condensation of the organic unsaturated silane. In any event, the carrier polymer should be substantially free of water. The carrier polymer of the invention is usually in the form of granules or granules in the form of pellets, the preferred form being pellets.

The carrier polymer of the silane crosslinker masterbatch used in the present invention is an ethylene-unsaturated ester copolymer, preferably EEA, EMMA having a comonomer content of 18 to 41% by weight, or a mixture thereof. Can be mentioned. If the comonomer content is less than 18% by weight, a desired silane impregnation amount cannot be obtained, and if it exceeds 41% by weight, blocking occurs during silane impregnation, resulting in poor workability. Considering silane impregnation, workability, economy and the like, EEA is preferred.

The catalyst masterbatch of the present invention can be produced by kneading a carrier polymer, a silanol condensation catalyst, an antioxidant and the like and granulating the mixture. Further, the melting point of the carrier polymer of the catalyst master batch must be higher than the melting point of the polyolefin-based base polymer. This causes a silane grafting reaction and a silanol condensation reaction at the time of extrusion, but the silanol condensation catalyst and the antioxidant in the catalyst masterbatch lower the crosslinking efficiency by inhibiting crosslinking in the silane grafting reaction. Therefore, by giving a difference in the melting point, the silane grafting reaction proceeds first, and then the silanol condensation reaction proceeds, whereby the inhibition of crosslinking can be prevented. Also, the catalyst masterbatch must be in particulate form and a solid compatible with the base polymer to be crosslinked. The catalyst masterbatch of the present invention is usually granulated in the form of granules or pellets, the preferred form being pellets.

The carrier polymer of the catalyst masterbatch used in the present invention is, for example, polyethylene, polypropylene, a copolymer of ethylene and an α-olefin, and the α-olefin is, for example, propylene of C _{3 to} C ₁₂ , Butene-1, pentene-1, octene-1, 4-methylpentene-1, 4-methylhexene
1,4,4-dimethylpentene-1, nonene-1, decene-1, undecene-1, dodecene-1, and the like, and mixtures thereof.

The silanol condensation catalyst of the present invention includes, for example, dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, stearin Lead acid, zinc stearate, cadmium stearate, barium stearate,
Organic metal compounds such as calcium stearate and the like can be mentioned. The amount of these additives may be 0.01 to 0.1% based on the total weight of the polymer in the silane-crosslinked polyolefin.
It is 2% by weight, preferably 0.02 to 0.1% by weight.
If the amount is less than 0.01% by weight, a sufficient crosslinking reaction does not proceed. If the amount exceeds 0.2% by weight, crosslinking occurs locally in the extruder at the time of extrusion, and the appearance is significantly deteriorated. Also, the silanol condensation catalyst must be added to the catalyst masterbatch. This is because the addition of the silane crosslinking master batch promotes the oligomerization due to the condensation of the silane and causes the appearance to deteriorate.

The antioxidant of the present invention is generally used when processing a polyolefin and is not particularly limited, but must be added to a catalyst masterbatch. This is because the addition of the silane crosslinking agent master batch inhibits crosslinking by radical scavenging. Even when other additives are added, additives that may inhibit crosslinking must be added to the catalyst masterbatch.

The amount of the masterbatch added is such that the total amount of the silane crosslinking agent masterbatch and the catalyst masterbatch is in the range of 3 to 15% by weight of the total amount of the whole composition. If it is less than 3% by weight, sufficient grafting does not occur, and
If the content is more than 10% by weight, molding failure occurs, and it is not economical.

As other additives, if desired, commonly used additives such as a neutralizer, an ultraviolet absorber, an antistatic agent, a pigment, a dispersant, a thickener, a metal deterioration inhibitor, a fungicide, A flow regulator, other inorganic fillers, or the like, or other synthetic resins can also be contained.

[0024]

Embodiments will be described below with reference to embodiments. << Manufacture of master batch of silane crosslinking agent >> First, carrier polymers (EEA (1), EEA (2), EEA (3), L-
LDPE) is charged into a closed-type supermixer mixer kept at 80 ° C., mixed by stirring, and preheated to 80 ° C. Next, a liquid mixture in which a free radical generator was dissolved in unsaturated silane was charged into a supermixer, and the carrier polymer was impregnated with stirring under a nitrogen pressure of 1 kg / cm ² . Other methods such as changing the preheating temperature and changing the nitrogen pressurization condition were also performed in the same manner as described above.

<< Production of Catalyst Masterbatch >> According to the compounding ratio shown in Table 2, the carrier polymer (HDP
E (1), HDPE (2), PP, LDPE), a silanol condensation catalyst, an antioxidant and the like were kneaded and granulated using a pressure kneader.

The raw materials used are as follows. (1) EEA (1): ethylene-ethyl acrylate copolymer (melting point: 90 ° C., EA content; 23% by weight) (2) EEA (2): ethylene-ethyl acrylate copolymer (melting point: 95 ° C., EA (3) EEA (3): ethylene-ethyl acrylate copolymer (melting point: 85 ° C., EA content: 50% by weight) (4) L-LDPE: linear low-density polyethylene (melting point:
(125 ° C., density: 0.924 g / cm ³ , MI: 3.0 g / 10 min) (5) VTMOS: vinyltrimethoxysilane (6) DCP: dicumyl peroxide (7) HDPE (1): high-density polyethylene (melting point: 130
° C, density: 0.950 g / cm ³ , MI: 5 g / 10 min) (8) HDPE (2): high-density polyethylene (melting point: 135
° C, density: 0.955 g / cm ³ , MI: 4 g / 10 min) (9) PP: polypropylene (block polymer, melting point: 1)
(10) LDPE: Low density polyethylene (melting point: 105 ° C, density: 0.925 g / cm ³ , MI; 1.5 g / 10 min) (11) MDPE: Medium density polyethylene (melting point: 110 ° C., a ^{density; 0.930g / cm 3, MI;} 1.0g / 10min) (12) DBTDL: dibutyltin dilaurate (13) antioxidant: phenolic antioxidant / Irganox 1010 (Ciba-Geigy (strain (14) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Chemical Industries, Ltd.)

The evaluation method is as follows. (15) Silane impregnation: The impregnation when the VTMOS / DCP liquid mixture was heated and stirred with a supermixer was evaluated. ：: good impregnating property, ×: impregnable. Also, silane impregnation time (min), silane impregnation yield (%), crushability of pellets, and blocking property during silane impregnation were evaluated. (16) Tape extrusion appearance: 50mmφ extruder 120-150-170-180-170 ℃ L / D: 20 Compression ratio 3.5 Tape die: width 100mm Rip interval 1mmt Evaluation: In order of ○ ＞ △ ＞ ×, ○ level Was passed. (17) Gel fraction (%): 120 ° C., 20 hours, xylene immersion method (18) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (19) Heat deformation ratio (%): According to JIS K 6723.

The polyolefin base polymer, the obtained silane crosslinking master batch and the catalyst master batch are mixed in the ratio shown in Table 3, the tape is extruded using an extruder, and further subjected to crosslinking treatment by immersion in warm water. Was. Using this extruded tape, the gel fraction, tensile strength, elongation, and heat deformation were evaluated.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

As is clear from the table, the silane crosslinking agent master batches shown in Examples 1 and 2 have excellent silane impregnation properties,
Further, the materials shown in Examples 3 to 7 using the same have good extrusion processability and show very excellent crosslinking properties, mechanical properties, and heat resistance. In contrast, all of the comparative examples do not have a balance between silane impregnation, extrudability, crosslinking properties, mechanical properties, and heat resistance.

[0033]

According to the present invention, a silane crosslinking agent masterbatch excellent in silane impregnation can be efficiently obtained, and by using this, excellent extrusion processability, crosslinking properties and mechanical properties can be obtained. And a silane-crosslinked polyolefin having excellent heat resistance can be obtained.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 255/00 C08L 23/08 C08L 51/06

Claims (9)

(57) [Claims] 1. A carrier polymer comprising an ethylene-unsaturated ester copolymer, comprising: (i) a polyolefin-based base polymer; and (ii) a silane crosslinking agent which is a liquid organic unsaturated silane containing a free radical generator. A silane crosslinking agent masterbatch impregnated at a temperature close to or below the melting point of the polymer, and (iii) a catalyst masterbatch containing a silanol condensation catalyst and an antioxidant are melted at a temperature higher than the crystal melting point of all polymers. A method for producing a silane-crosslinked polyolefin, comprising mixing, reacting, and then contacting with water to crosslink. 2. The ethylene-unsaturated ester copolymer has a comonomer content of 18 to 41% by weight, and the organic unsaturated silane is added in an amount of 10 to 4% based on the carrier polymer.
The method for producing a silane crosslinking agent master batch according to claim 1, wherein the amount is 0% by weight. 3. The silane according to claim 1, wherein the ethylene-unsaturated ester copolymer comprises an ethylene-ethyl acrylate copolymer, an ethylene-methyl methacrylate copolymer, or a mixture thereof. A method for producing a crosslinking agent master batch. 4. The organic unsaturated silane comprises vinyltrimethoxysilane or vinyltriethoxysilane, and the free radical generator is dicumyl peroxide or α, α'-bis (t-butylperoxydiisopropyl) benzene. The method for producing a silane-crosslinked polyolefin according to claim 1 or 2, wherein 5. The carrier polymer is preheated to a temperature 5 to 30 ° C. lower than its melting point, and 5 to 30 ° C. lower than its melting point.
A silane cross-linking agent is charged into a closed mixer kept at a low temperature of 0 ° C. while stirring and charged, and then the carrier polymer is impregnated with the silane cross-linking agent under pressure. 5. The method for producing a silane-crosslinked polyolefin according to 2, 3, or 4. 6. When impregnating the carrier polymer with a silane crosslinking agent under pressure, the pressure condition is 0.1 to 10 kg / kg.
Claim 1, 2, 3, 4 or 5 production method of silane-crosslinked polyolefin wherein a is cm ^2. 7. The method according to claim 1, wherein the carrier polymer is impregnated with a silane crosslinking agent under nitrogen pressure.
7. The method for producing a silane-crosslinked polyolefin according to 2, 3, 4, 5, or 6. 8. The catalyst master batch according to claim 1, wherein the carrier polymer comprises polyethylene, polypropylene, a copolymer of ethylene and α-olefin, or a mixture thereof, wherein the melting point of the carrier polymer is higher than that of the polyolefin base polymer. A method for producing a silane-crosslinked polyolefin. 9. The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the total amount of the silane crosslinking agent masterbatch and the catalyst masterbatch is 3 to 15% by weight.