JPH101520A - Production of flame-retardant silane-cross-linked polyolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flame-retardant silane-cross linked polyolefin excellent in extrudability, cross-linking properties, mechanical properties, frame retardance, and heat resistance by melt mixing and reacting a specific flame- retardant polyolefin with a specific carrier polymer and bringing the reaction product into contact with water to effect cross-linking. SOLUTION: This cross-linked polyolefin is obtd. by melt mixing and reacting a flame-retardant polyolefin with a carrier polymer and bringing the reaction product into contact with water to effect cross-linking. The flame-retardant polyolefin is prepd. by compounding 100 pts.wt. α-olefin homo- or copolymer having a density of 0.92g/cm<3> or lower with 50-100 pts.wt. aluminum hydroxide having an average particle size of 0.5-3μm, a silane coupling agent, a silicone deriv., 0.5-10 pts.wt quick lime surface-treated with a fatty acid (metal salt), and a silanol condensation catalyst. The carrier polymer contains an unsatd. organosilane represented by the formula: RR' SiY2 (wherein R is a monovalent olefinically unsatd. hydrocarbon group; Y is a hydroyzable org. group; and R' is a monovalent hydrocarbon group or Y) and a free-radical generator and does not contain water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silane cross-linking of a flame-retardant polyolefin containing a silanol condensation catalyst and quicklime, in one step by using a carrier polymer containing a high concentration of an organic unsaturated silane or the like. It relates to a silane crosslinking method to be produced.

[0002]

2. Description of the Related Art In order to impart flame retardancy to a polyolefin composition which has been widely used in coatings of electric wires and cables, hoses, sheets and injection products, a halogen compound and antimony trioxide are added to the polyolefin. This has been achieved by the addition. However, these compositions are unfavorable because they are smoke compositions because they are halogen compositions and because the metal is corroded. Under such circumstances, attention has been paid to inorganic flame retardants using hydrated metal compounds with extremely low smoke emission properties. In recent years, in order to impart flame retardancy, resin composites containing magnesium hydroxide, aluminum hydroxide, and the like have been put to practical use. However, in these flame retardant resin compositions, smoke emission can be prevented. In addition, there is a problem that a so-called drip phenomenon occurs in which the resin composition melts and drops during combustion, or the shape retention at high temperatures is poor.

In order to improve this, in addition to flame retardancy, in order to improve heat resistance, there is a method of crosslinking, which is disclosed in, for example, JP-B-57-24373 and JP-B-57-26620. I have. However, as described here, large-scale crosslinking devices such as chemical crosslinking and electron beam crosslinking are required, and the cost of the equipment itself, the subsequent operation and maintenance costs, etc. increase, and the cost of the composition increases. Was invited. Also, JP-A-60-10112
9, as seen in JP-A-60-147463, a flame-retardant cross-linked composition characterized by being finally cross-linked by adding a flame retardant to a silane-grafted polyolefin resin having silane grafted in advance. In this case, the degree of crosslinking of the silane-grafted polyolefin resin could not be increased in order to suppress early crosslinking when the flame retardant was mixed with the silane-grafted polyolefin resin and kneaded, and the heat resistance was insufficient.

This method also involves at least two reaction 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. Also, an extruder requires an expensive and special type having a large L / D to uniformly disperse a small amount of additives, and an economic problem cannot be avoided. In addition, very high technology is also required for extrusion, and a flame-retardant type has not been commercialized.

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. However, in this method, the solid carrier polymer is a porous polymer or EVA, and additives such as a silanol condensation catalyst and an antioxidant are introduced into the solid carrier polymer in addition to the silane and the free radical generator. For this reason, there has been a problem that crosslinking efficiency and storage stability are inferior due to oligomerization by silane condensation or crosslinking inhibition by radical scavenging. In addition, there is no description about the flame retardant type here.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems. In the silane crosslinking of a flame retardant polyolefin containing a silanol condensation catalyst and quicklime, a carrier containing a high concentration of an organic unsaturated silane or the like is used. An object of the present invention is to provide a silane cross-linking method for producing a flame-retardant silane cross-linked polyolefin in one step using a polymer.

[0007]

According to the present invention, (i) the average particle size is 0.1 to 100 parts by weight of an α-olefin homopolymer or copolymer having a density of 0.92 g / cm ³ or less. 5
50 to 200 parts by weight of aluminum hydroxide of 3 μm and one or more silane coupling agents, silicone derivatives,
Quicklime with surface treatment with fatty acid or fatty acid metal salt 0.5 to
A flame-retardant polyolefin obtained by adding 10 parts by weight and a silanol condensation catalyst, and (ii) a general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, R Is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y), and a substantially water-free carrier polymer containing a free radical generator. A method for producing a flame-retardant silane cross-linked polyolefin, which is melt-mixed and reacted at a temperature higher than the crystal melting point of the base polymer of the flame-retardant polyolefin, and then contacted with water to cross-link. The copolymer is a homopolymer of an α-olefin such as ethylene or propylene, or a crystalline block or random copolymer of an α-olefin and another α-olefin. Or copolymers thereof with polar monomers such as vinyl acetate, maleic anhydride, acrylic acid, etc., and mixtures thereof, wherein the carrier polymer is ethylene-ethyl acrylate copolymer (EEA); An ethylene-methyl methacrylate copolymer (EMMA), at least one vinyl aromatic compound-based polymer block,
Is a polymer selected from the group consisting of hydrogenated block copolymers obtained by hydrogenating a block copolymer consisting of polymer blocks mainly composed of conjugated diene compounds and a mixture thereof, and the addition of a carrier polymer. The amount is 1
This is a method for producing a flame-retardant silane-crosslinked polyolefin having an average particle size of quicklime of 1 to 5 μm in an amount of 5% by weight.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The α-olefin homopolymer or copolymer used in the present invention may be a homopolymer of α-olefin such as ethylene or propylene, or a crystalline block or random copolymer of α-olefin and another α-olefin. Polymers such as crystalline propylene-ethylene block copolymer, ethylene-butene-1 random copolymer, propylene-butene-1 random copolymer, or α-olefin, vinyl acetate, maleic anhydride And copolymers with polar monomers such as acrylic acid (including graft copolymers)
And a mixture of these having a density of 0.92 g / cm
³ or less. If the density is greater than 0.92 g / cm ^3, there is a problem that the acceptability of the flame retardant is poor and the mechanical properties are reduced.

The aluminum hydroxide used in the present invention has an average particle size of 0.5 to 3 μm from the viewpoint of processability during extrusion.
Are preferred. Further, a material which has been subjected to a surface treatment with a silane coupling agent, a silicone derivative, a fatty acid or a fatty acid metal salt can also be used. 50 aluminum hydroxide
When it is blended from 200 parts by weight to 200 parts by weight, it is compatible with or reacts with a low-density low-crystalline polymer, and a composition excellent in low-temperature properties, flexibility and processability can be easily formed even when highly filled. However, if it is less than 50 parts by weight, its flame retardant effect will be significantly reduced. If it exceeds 200 parts by weight, the flame retardancy is remarkably improved, but the mechanical properties such as flexibility and low-temperature properties are reduced, and the workability is extremely deteriorated. If the average particle size of the aluminum hydroxide is smaller than 0.5 μm, secondary agglomeration is likely to occur and it is difficult to manufacture.
If it is larger than μm, the extrusion processability is inferior.

The quicklime used in the present invention has been subjected to a surface treatment with a silane coupling agent, a silicone derivative, a fatty acid or a fatty acid metal salt. The silane coupling agent has a reactive group that reacts with an inorganic substance (a methoxy group, an ethoxy group, a carboxyl group, a cellosolve group, etc.) at one end of the molecule, and generally has a trifunctional group. In many cases, it may be bifunctional or monofunctional. On the other end, a reactive group (vinyl group, epoxy group,
(Methacrylic group, amino group, mercapto group, etc.) whose main chain has an alkoxy oligomer as a skeleton.

The silicone derivative is a type in which a methyl group of dimethylpolysiloxane is partially substituted with various organic groups, and various modified organic groups include α-methylstyrene group, α-olefin group, polyether group, Compatibility of alcohol group, fluoroalkyl group, etc., hydrophilicity, lubricity,
Modification group for the purpose of improving water repellency, amino group, mercapto group, epoxy group, carboxyl group, etc.Reactivity, modification group for the purpose of hygroscopicity, higher fatty acid, carnauba, mold release substituted with amide And various modified group derivatives such as a modified group for the purpose of polishing.

The fatty acid includes saturated and unsaturated fatty acids, and refers to fatty acids having 6 to 22 carbon atoms, and particularly includes C ₁₈ stearic acid and oleic acid. Examples of the fatty acid metal salt include a metal soap in which the above fatty acid is bonded to a metal, and particularly include sodium stearate, potassium stearate, sodium oleate, potassium oleate, and the like. Of course, fatty acids having a side chain bonded to a metal are effective regardless of whether they are linear or unsaturated.

This quicklime is added to reduce the amount of water adhering to the flame-retardant polyolefin. This is because if there is moisture attached to the flame-retardant polyolefin, early crosslinking occurs in the silane crosslinking step. It has been confirmed that the amount of water adhering to cause this early crosslinking is about 100 ppm or more.
5 to 10 parts by weight must be added. If the amount is less than 0.5 part by weight, the amount of adhering water becomes 100 ppm or more, causing early crosslinking. On the other hand, if it exceeds 10 parts by weight, there is no effect of reducing the amount of adhering water, and the mechanical properties may be lowered. Also, quick lime having an average particle diameter of 1 to 5 μm is preferable in order to obtain excellent dispersibility in the flame-retardant polyolefin and to obtain a more uniform adsorbed moisture absorbing effect. If the average particle size is smaller than 1 μm, secondary aggregation is likely to occur and the production is difficult. If the average particle size is larger than 5 μm, the dispersibility is poor and the adsorbed water absorbing effect is poor.

The silanol condensation catalyst of the present invention includes dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, and stearic acid. Organic metal compounds such as lead, zinc stearate, cadmium stearate, barium stearate, calcium stearate and the like can be mentioned. The amount of these additives is 0.01 to 0.1% by weight, preferably 0.03 to 0.07% by weight, based on the total weight of the flame-retardant silane crosslinked polyolefin. 0.01% by weight
If it is less than 0.1%, a sufficient crosslinking reaction does not proceed, while if it exceeds 0.1% by weight, crosslinking is locally advanced in the extruder at the time of extrusion, and the appearance is remarkably deteriorated. Also, the silanol condensation catalyst must be added to the flame-retardant polyolefin. This is because the addition of the carrier polymer promotes the oligomerization due to the condensation of the silane and causes the appearance to deteriorate.

[0015] The organic unsaturated silane of the present invention is grafted onto the base resin so as to be a cross-linking point between the base resins. Examples of the organic unsaturated silane used in the present invention include compounds 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 wherein} R 'is the same as Y, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, Allyltriethoxysilane and the like can be mentioned. The amount of these additives is from 0.1 to 2% by weight, preferably from 0.4 to 1% by weight, based on the total weight of the flame-retardant silane-crosslinked polyolefin.
It is. When the amount is less than 0.1% by weight, sufficient grafting does not occur. When the amount is more than 2% by weight, molding failure occurs and it is not economical.

The free radical generator of the present invention acts as an initiator for a 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. The addition amount of these is 0.01 to 0.1% by weight, preferably 0.02 to 0.0% by weight based on the total weight of the flame-retardant silane crosslinked polyolefin.
5% by weight. If the amount is less than 0.01% by weight, a sufficient silane grafting reaction does not proceed.

The free radical generator and silane can be added to the carrier polymer by swelling the carrier polymer of the present invention with a liquid mixture in which the free radical generator is dissolved in silane. At this time, the carrier polymer must be preheated to add a high concentration of silane, but the temperature must be lower than the crystal melting point so that the polymer does not melt. The carrier polymer must also be in particulate form and be solid compatible with the cross-linkable flame retardant polyolefin and silane. Compatible means that the carrier polymer must not readily react with the silane and must be dispersible or soluble in the flame retardant polyolefin. Suitable carrier polymers are non-hygroscopic. That is, it is preferred that the water absorption be relatively slow to minimize the potential for premature hydrolysis and condensation of the 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 used in the present invention includes, for example, ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), and a polymer mainly composed of at least one vinyl aromatic compound. A hydrogenated block copolymer obtained by hydrogenating a block copolymer composed of a united block and a polymer block mainly composed of at least one conjugated diene compound, for example, a hydrogenated styrene-isoprene block copolymer (SEPS) ), Hydrogenated styrene-butadiene block copolymer (SEBS) and the like, and mixtures thereof. The amount of carrier polymer added is 1
-5% by weight. When the amount is less than 1% by weight, sufficient grafting does not occur, and when the amount exceeds 5% by weight, molding failure occurs and it is not economical.

As other additives for the flame-retardant polyolefin, if desired, additives usually used, for example, antioxidants, neutralizers, ultraviolet absorbers, antistatic agents, pigments, dispersants, thickeners, metals Deterioration inhibitors, fungicides, flow regulators, etc., or other synthetic resins can also be included.

[0021]

Embodiments will be described below with reference to embodiments. << Production of Flame-Retardant Polyolefin >> According to the mixing ratios shown in Tables 1 and 2, the respective components were mixed, kneaded at a temperature of 160 to 180 ° C. using a Banbury, and granulated. << Production of Carrier Polymer >> According to the compounding ratio shown in Table 3, the carrier polymer is first charged into a super mixer, mixed with stirring, and preheated to 80 ° C. Next, a liquid mixture in which a free radical generator was dissolved in an unsaturated silane was charged into a supermixer, and the carrier polymer was impregnated with stirring for 20 minutes.

The raw materials used are as follows. (1) D9052: Copolymer of ethylene and α-olefin / Softrex D9052 (manufactured by Nippon Petrochemical Co., Ltd.),
Density: 0.905 g / cm ³ (2) P-0480: copolymer of ethylene and α-olefin / Tafmer P-0480 (manufactured by Mitsui Petrochemical Co., Ltd.); density: 0.87 g / cm ³ (3) hydroxylation Aluminum: Heidilite H42M (manufactured by Showa Denko KK) (4) Quicklime (1): Stearic acid-treated product with an average particle size of 3 μm (5) Quicklime (2): Average particle size of 10 μm, stearic acid-treated product (6) DBTDL: dibutyltin dilaurate (7) Antioxidant: phenolic antioxidant / Irganox 1010 (manufactured by Ciba Geigy) (8) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Chemical Industries, Ltd.) (9) EEA: ethylene-ethyl acrylate copolymer (E
(A content: 23% by weight) (10) SEPS: hydrogenated styrene-isoprene block copolymer (styrene content: 30% by weight) (11) L-LDPE: linear low-density polyethylene (density;
0.924 g / cm ³ , MI: 3.0 g / 10 min) (12) VTMOS: vinyltrimethoxysilane (13) DCP: dicumyl peroxide

The evaluation method is as follows. (14) Water content (ppm): Karl Fischer method (150
(゜ C, 30 minutes) (15) Silane impregnating property: The impregnating property when the VTMOS / DCP liquid mixture was heated and stirred with a super mixer was evaluated. ○: good impregnation, ×: impregnable (16) Tape extrusion appearance: 50mmφ extruder 120-150-170-180-170 ℃ L / D: 20, compression ratio 3.5, tape die: width 100mm, lip interval 1mmt Evaluation : The order of △>△> × was set, and the level of ○ was judged to be acceptable. (17) Oxygen index: according to JIS K 7201. (18) Gel fraction (%): 120 ° C., 20 hours, xylene immersion method (19) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (20) Hot set: According to IEC-540A. ○: passed, ×: failed

The resulting flame-retardant polyolefin and the carrier polymer were mixed at the ratios shown in Tables 4 and 5, and a tape was extruded using an extruder, followed by immersion in warm water to perform a crosslinking treatment. Using this extruded tape, the gel fraction, tensile strength, elongation, and hot setting were evaluated. The extruded tape was pressed to evaluate the oxygen index.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5] As is clear from the table, the materials shown in Examples 1 to 4 have good extrusion processability and show very excellent crosslinking properties, mechanical properties, flame retardancy and heat resistance. In contrast, all of the comparative examples do not have a balance between extrudability, cross-linking properties, mechanical properties, flame retardancy and heat resistance.

[0030]

According to the present invention, a flame-retardant silane-crosslinked polyolefin having excellent extrudability and excellent crosslinking properties, mechanical properties, flame retardancy and heat resistance can be obtained.

Claims (5)

[Claims] (1) α- having a density of 0.92 g / cm ³ or less;
50 to 200 parts by weight of aluminum hydroxide having an average particle size of 0.5 to 3 μm and at least one silane coupling agent, silicone derivative, fatty acid or fatty acid based on 100 parts by weight of olefin homopolymer or copolymer A flame-retardant polyolefin obtained by adding 0.5 to 10 parts by weight of quick lime surface-treated with a metal salt and a silanol condensation catalyst, and (ii) a general formula RR′SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group) , Y is a hydrolyzable organic group, and R 'is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y)
Is melt-mixed with a substantially water-free carrier polymer containing an organic unsaturated silane represented by and a free radical generator at a temperature higher than the crystal melting point of the base polymer of the flame-retardant polyolefin, and then reacted with water. A method for producing a flame-retardant silane cross-linked polyolefin, which comprises cross-linking by contacting with polyolefin. 2. The α-olefin homopolymer or copolymer is an α-olefin homopolymer such as ethylene or propylene, or a crystalline block or random of an α-olefin and another α-olefin. Copolymer, or α-olefin-based, vinyl acetate, maleic anhydride,
The method for producing a flame-retardant silane-crosslinked polyolefin according to claim 1, which is a copolymer with a polar monomer such as acrylic acid or a mixture thereof. 3. A polymer block mainly comprising an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), at least one vinyl aromatic compound,
2. A hydrogenated block copolymer obtained by hydrogenating a block copolymer composed mainly of at least one conjugated diene compound and a mixture thereof. Or the method for producing a flame-retardant silane-crosslinked polyolefin according to 2. 4. The amount of the carrier polymer added is from 1 to 5
4. The method for producing a flame-retardant silane-crosslinked polyolefin according to claim 1, wherein the amount is% by weight. 5. The method for producing a flame-retardant silane-crosslinked polyolefin according to claim 1, wherein said quick lime has an average particle size of 1 to 5 μm.