JPH0940713A - Method for producing silane-modified polyolefin - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a method for producing a silane-modified polyolefin capable of increasing the gel fraction to improve various properties and suppressing the scorch phenomenon. SOLUTION: A polyolefin, an olefinically unsaturated silane compound represented by the following general formula (1), a free radical generator, a silanol condensation catalyst, and a saturated compound represented by the following general formula (2) per 100 parts by weight of the polyolefin. A method for producing a silane-modified polyolefin, which comprises heat-mixing and reacting a composition containing 0.01 to 5 parts by weight of a silane compound in an extruder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a silane-modified polyolefin.

[0002]

2. Description of the Related Art Silane-modified polyolefin undergoes a cross-linking reaction when it comes into contact with water, and has various properties such as mechanical strength, heat resistance, creep resistance, environmental stress crack resistance, chemical resistance, etc. Since it is significantly improved in comparison, it is preferably used as a raw material for covered electric wires, hot water supply pipes, flame-retardant materials and the like.

Examples of the method for bringing the silane-modified polyolefin into contact with water to crosslink it include high-temperature hot-water treatment and immersion in water. These water-crosslinking steps impart the silane-modified polyolefin to a desired shape. It is generally provided after the shaping step of shaping.

From the viewpoint of productivity, an attempt has been made to disperse a silanol condensation catalyst as a crosslinking reaction accelerator in the silane-modified polyolefin in advance in order to shorten the crosslinking time in the water crosslinking step as much as possible. In Japanese Patent Laid-Open No. 53-65345, for example, a liquid containing a silane compound, a radical generator and a siloxane condensation catalyst is added to polyolefin pellets, and extrusion molding is performed while heating and reacting. A cross-linking system for polyolefins has been proposed which is characterized in that a molded product is brought into contact with water to cross-link it.

However, in the crosslinking method proposed above, the water adsorbed on the polyolefin penetrates into the extruder, and the hydrolysis reaction of the unsaturated silane graft-bonded to the polyolefin causes the siloxane condensation reaction and the water content at a high temperature in the extruder. The so-called scorch phenomenon, which promotes early crosslinking in the extruder, tends to occur, and the appearance of the obtained silane-modified polyolefin molded article is impaired, and the fusion property with the peripheral portion is reduced to cause cracking or breakage. There is a problem that it is easy to cause.

In order to address the above problems, Japanese Patent Laid-Open No. 53-
In Japanese Patent No. 69245, a polyolefin, a specific silane, and a free radical generator capable of generating a free radical in the polyolefin are mixed in a high temperature kneading zone of an extruder at a temperature of about 190 to 220 ° C. Silane is graft-bonded to the grafted polyolefin, and the silanol condensation catalyst is mixed with the grafted polyolefin at a temperature of about 120 to 160 ° C. in the next kneading zone following the kneading zone, and the mixture is extruded from the extrusion head of the extruder. A method for extruding / crosslinking a polyolefin, characterized in that the extruded product is crosslinked in the presence of water by a hydrolysis reaction of the bound silane, has been proposed.

However, even in the extrusion / crosslinking method proposed above, it is difficult to keep an extruder having a continuous structure having an inlet portion and an outlet portion in a completely airtight state, and a trace amount of water penetrates into the extruder. However, the scorch phenomenon cannot be completely suppressed, and the above problems cannot be completely solved.

On the other hand, in order to improve various properties such as mechanical strength, heat resistance, and creep resistance of the silane-modified polyolefin molded article, the gel fraction of the silane-modified polyolefin (the proportion of insoluble heat xylene), in other words, For example, it is desirable to increase the degree of cross-linking.For example, a method of increasing the content of unsaturated silane can be adopted.However, if the content of unsaturated silane is increased, premature cross-linking in the extruder is promoted and the scorch The phenomenon is more likely to occur. That is, there is a contradictory relationship between increasing the gel fraction to improve various properties and suppressing the scorch phenomenon, and it is extremely difficult to achieve both at the same time.

[0009]

In order to solve the above-mentioned conventional problems, the present invention is capable of increasing the gel fraction to improve various properties, and at the same time, is capable of suppressing the scorch phenomenon. It is an object to provide a manufacturing method of

The method for producing a silane-modified polyolefin according to the present invention comprises a polyolefin, an olefinically unsaturated silane compound represented by the following general formula (1), a free radical generator, a silanol condensation catalyst, and
A composition comprising 0.01 to 5 parts by weight of a saturated silane compound represented by the following general formula (2) with respect to 100 parts by weight of the above polyolefin is heated and mixed in an extruder to cause a reaction. The above-mentioned subject is achieved.

Embedded image (In the formula, R ¹ represents a monovalent olefinically unsaturated hydrocarbon group or a monovalent olefinically unsaturated hydrocarbonoxy group, Y represents a hydrolyzable organic group, and R ² represents a group Y or hydrogen. Group or a saturated aliphatic hydrocarbon group)

Embedded image (In the formula, R ³ represents a linear or branched saturated hydrocarbon group having 1 to 30 carbon atoms, Y represents an organic group capable of being hydrolyzed, and R ⁴ is a group Y or a hydrogen group or 1 to 1 carbon atoms. Represents 30 linear or branched saturated hydrocarbon groups)

The polyolefin used in the method for producing a silane-modified polyolefin according to the present invention is a (co) polymer of an olefinic monomer and is not particularly limited, and examples thereof include low density polyethylene, high density polyethylene, Polyethylene such as linear low-density polyethylene, polypropylene, ethylene-propylene copolymer,
Examples thereof include an ethylene-propylene-diene terpolymer, an ethylene-butene copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, and a chlorinated polyethylene. One or two kinds of them are listed. The above are preferably used, but among them, one kind or two or more kinds of polyethylene such as low density polyethylene, high density polyethylene, linear low density polyethylene and polypropylene, and polypropylene are more preferably used. The "(co) polymer" referred to here
Means a "polymer" or a "copolymer".

The olefinically unsaturated silane compound used in the method for producing a silane-modified polyolefin according to the present invention is represented by the following general formula (1).

Embedded image

In the above general formula (1), the group R ¹ represents a monovalent olefinically unsaturated hydrocarbon group or a monovalent olefinically unsaturated hydrocarbonoxy group, and is not particularly limited, but for example, , Vinyl group, allyl group, isopropenyl group, butenyl group, cyclohexenyl group, cyclopentadienyl group, γ- (meth) acryloxypropyl group and the like, and they are preferably used.

In the above general formula (1), the group Y represents a hydrolyzable organic group and is not particularly limited.
For example, methoxy group, ethoxy group, formyloxy group,
Examples thereof include an acetoxy group, a propionyloxy group, an alkylamino group, and an arylamino group, and one type or two or more types thereof are preferably used.

Further, in the above general formula (1), the group R ² is a hydrolyzable organic group similar to the group Y or a hydrogen group, or an aliphatic saturated carbon group such as a methyl group, an ethyl group, a propyl group and a decyl group. Represents a hydrogen group.

Specific examples of the olefinically unsaturated silane compound represented by the above general formula (1) include, but are not limited to, vinyltrimethoxysilane, vinyltriethoxysilane and vinyltriacetoxysilane. One or more of these are preferably used.

In the method for producing a silane-modified polyolefin according to the present invention, the content of the olefinically unsaturated silane compound in the composition is not particularly limited, but the olefinic content is 100 parts by weight of the polyolefin. The unsaturated silane compound is preferably 0.5 to 10 parts by weight, and more preferably 0.7 to 5 parts by weight.

If the content of the olefinically unsaturated silane compound is less than 0.5 parts by weight based on 100 parts by weight of the polyolefin, the gel fraction of the obtained silane-modified polyolefin will not be sufficiently high, so that mechanical strength, heat resistance, If various properties such as creep resistance are not sufficiently improved, and if it exceeds 10 parts by weight on the contrary, the melt viscosity of the obtained silane-modified polyolefin becomes too high, and the extruder is overloaded and the workability is deteriorated. Elongation rate and heat fusion property are reduced.

The free radical generator used in the method for producing a silane-modified polyolefin according to the present invention is not particularly limited, as long as it is any compound generally used in the grafting reaction of polyolefin. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butylperoxyacetate, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxide) (Oxy) hexane, di-t-butylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 and other organic peroxides, azobisisobutyronitrile, dimethylazodiisobutene Examples include azo compounds such as tylate, and one or more of these are preferably used. Among them, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butylperoxide, 2,5-dimethyl-2,5-di ( One or more of t-butylperoxy) hexyne-3 and the like are more preferably used.

In the method for producing a silane-modified polyolefin according to the present invention, the content of the above-mentioned free radical generator in the composition is not particularly limited, but the free radical generation is based on 100 parts by weight of the above-mentioned polyolefin. The amount of the agent is preferably 0.01 to 5 parts by weight, and more preferably 0.02 to 2 parts by weight.

If the content of the free radical generator is less than 0.01 parts by weight based on 100 parts by weight of the polyolefin, the desired gel fraction cannot be obtained because the grafting reaction does not proceed sufficiently, and conversely 5 parts by weight is used. If it exceeds the above range, the free radical sites in the polyolefin become too large and so-called peroxide cross-linking proceeds, so that the scorch phenomenon occurs, the surface smoothness decreases, the viscosity increases abnormally, and the workability deteriorates.

The silanol condensation catalyst used in the method for producing the silane-modified polyolefin according to the present invention is not particularly limited as long as it is any compound generally used as a catalyst for promoting dehydration condensation between silanols of silane. Although not limited to, for example, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, cobalt naphthenate, lead naphthenate,
Examples thereof include compounds such as ethylamine, dibutylamine, hexylamine and pyridine, inorganic acids such as sulfuric acid and hydrochloric acid, organic acids such as toluenesulfonic acid, acetic acid, stearic acid and maleic acid. One or more of these may be used. It is preferably used, but dibutyltin dilaurate is more preferably used.

In the method for producing a silane-modified polyolefin according to the present invention, the content of the silanol condensation catalyst in the composition is not particularly limited, but the silanol condensation catalyst is 0 parts by weight based on 100 parts by weight of the above-mentioned polyolefin. It is preferably 0.001 to 5 parts by weight, and more preferably 0.005 to 1 part by weight.

When the content of the silanol condensation catalyst is less than 0.001 part by weight based on 100 parts by weight of the polyolefin, the catalyst function is not sufficiently exhibited, so that the crosslinking step requires a long time, and conversely, when it exceeds 5 parts by weight. , Scorch phenomenon occurs due to premature crosslinking in the extruder.

The saturated silane compound used in the method for producing a silane-modified polyolefin according to the present invention is represented by the following general formula (2).

[Chemical 6]

In the general formula (2), the group R ³ has 1 to 1 carbon atoms.
30 linear or branched saturated hydrocarbon groups, which are not particularly limited, and include, for example, methyl group, ethyl group, propyl group, isobutyl group, n-butyl group, hexyl group, octyl group, 2 -Ethylhexyl group, decyl group, dodecyl group and the like are mentioned and are preferably used.

In the general formula (2), the group Y represents the same hydrolyzable organic group as the group Y in the general formula (1) representing the above-mentioned olefinically unsaturated silane compound.

Further, in the general formula (2), the group R ⁴ is a hydrolyzable organic group or hydrogen group similar to the group Y, or a linear group having 1 to 30 carbon atoms similar to the group R ³ or It represents a branched saturated hydrocarbon group.

Specific examples of the saturated silane compound represented by the general formula (2) include, but are not limited to, isobutyltrimethoxysilane, hexyltrimethoxysilane and decyltrimethoxysilane.
One or more of these are preferably used.

In the saturated silane compound represented by the above general formula (2), the hydrolyzable organic group of the saturated silane compound captures the water invading into the extruder and is graft-bonded to the olefinically unsaturated silane compound. Since it protects the hydrolyzable organic group, it exerts the function of suppressing the progress of the early crosslinking reaction in the extruder even in the coexistence of the silanol condensation catalyst. Further, since a part of the saturated silane compound is graft-bonded to the polyolefin, it participates in the cross-linking reaction in the post-treatment step (eg, hot water treatment step) after being discharged from the extruder, and functions to increase the gel fraction. Also exerts.

In the method for producing a silane-modified polyolefin according to the present invention, the saturated silane compound is contained in an amount of 0.01 to 5 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the above-mentioned polyolefin. Need to be present.

When the content of the saturated silane compound is less than 0.01 parts by weight based on 100 parts by weight of the polyolefin,
It is not possible to fully capture the water that has entered the extruder,
Since the function of suppressing the progress of the early crosslinking reaction in the extruder is not sufficiently exhibited, the scorch phenomenon occurs, and the function of increasing the gel fraction becomes insufficient.

On the other hand, when the content of the saturated silane compound is more than 5 parts by weight with respect to 100 parts by weight of the polyolefin, the melt viscosity of the composition is rapidly increased and the extruder is overloaded to deteriorate workability. The discharged material causes a so-called melt fracture phenomenon, and the surface smoothness and the like are remarkably reduced.

The composition used in the method for producing a silane-modified polyolefin according to the present invention contains, in addition to the above-mentioned essential components, an antioxidant, a stabilizer and an ultraviolet ray, if necessary, within a range not impairing the object of the present invention. One or more kinds of various additives such as an absorbent, an organic or inorganic filler, a pigment or a dye, and a processing aid may be contained.

The extruder used in the method for producing a silane-modified polyolefin according to the present invention is not particularly limited and may be an extruder generally used in general.
A single-screw extruder, a twin-screw extruder, a multi-screw extruder having three or more screws, and the like can be mentioned, and any of them is preferably used.

The above single-screw extruder is not particularly limited, but it is not limited to an extruder having a general full flight type screw, but an extruder having a discontinuous flight type screw, a pin barrel, a mixing head and the like. A machine and the like are also included, and any of them is preferably used.

Further, as the above twin-screw extruder,
Although not particularly limited, a meshing same-direction rotary extruder, a meshing different-direction rotary extruder, a non-meshing different-direction rotary extruder, and the like are mentioned, and any of them is preferably used.

The shape of the above-mentioned screw is not particularly limited, but it is preferable that the same-direction rotating type is a two- to three-thread type, and the different-direction rotating type is a two- to eight-thread type.
It may have a screw element such as a kneading disc, a seal ring, a reverse screw, and a rotor around the full flight type, and it may be either a parallel screw type or a conical screw type. May be.

Among the various screw type extruders mentioned above,
Considering the kneading performance and the like, a meshing (self-wiping) co-rotating twin-screw extruder is more preferably used.

Further, in the present invention, a die having a desired shape is installed at the tip of the extruder, and the obtained silane-modified polyolefin is shaped into a desired shape in one step.
The mixing and molding may be performed continuously to simplify the process.

In the present invention, the method of introducing the olefinically unsaturated silane compound, the free radical generator, the silanol condensation catalyst and the saturated silane compound into the extruder is not particularly limited, and each of them may be introduced alone. Alternatively, two or more of these may be charged in a state of being preliminarily stirred and mixed, or one or more of these may be charged in a state of being impregnated with a polyolefin in advance. Further, the place of charging into the extruder is not particularly limited.

The extrusion operating conditions in the present invention are not particularly limited. For example, the screw rotation speed, the extrusion amount, the cylinder set temperature, etc. are taken into consideration in the residence time in the extruder, the kneading degree, the parison strength at the time of molding, etc. Therefore, for example, a vacuum vent function may be added to remove residual water and impurities.

The method for producing the silane-modified polyolefin according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows an example of an extruder capable of ensuring an appropriate grafting reaction time and suppressing the scorch phenomenon.

In the production method according to the present invention, for example, an olefinic unsaturated silane compound, a free radical generator and a saturated silane compound which have been mixed by stirring in advance are used from a silane solution tank 4 using a chemical gear pump 5 with a screw feeder with a hopper. At the same time as the polyolefin supplied from 3 is charged into the extruder 1 through the charging port 2,
The free radical generator is decomposed in the former grafting reaction zone a set to a temperature of 220 ° C., and the olefinically unsaturated silane compound is grafted to the polyolefin. At this time, the water that has entered the extruder 1 is captured by the saturated silane compound. Then, after the silanol condensation catalyst was press-fitted from the silanol catalyst tank 6 using the plunger pump 7 into the catalyst kneading zone b in the latter stage, which was set at a low temperature of 120 to 190 ° C. to suppress the progress of the early crosslinking reaction. The desired silane-modified polyolefin and molded product can be obtained by discharging the silane-modified polyolefin in which the silanol condensation catalyst is dispersed from the die 8 having a desired shape, shaping and cooling.

(Function) According to the production method of the present invention, the hydrolyzable organic group possessed by the saturated silane compound captures the water invading into the extruder, and the hydrolyzable organic group possessed by the olefinically unsaturated silane compound can be hydrolyzed. Since the organic group is protected, the progress of the early crosslinking reaction in the extruder is suppressed even in the presence of the silanol condensation catalyst. Further, since a part of the saturated silane compound is graft-bonded to the polyolefin, it participates in the cross-linking reaction in the post-treatment step (for example, hot water treatment step) after being discharged from the extruder, thereby increasing the gel fraction.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION In order to explain the present invention in more detail, examples will be given below. In the examples, “parts” means “parts by weight”.

(Example 1)

( 1) Preparation of silane solution As shown in Table 1, 1 part of vinyltrimethoxysilane (trade name "Cila Ace S210", manufactured by Chisso Co.) as an olefinically unsaturated silane compound and 2, as a free radical generator. 0.08 parts of 5-dimethyl-2,5-di (t-butylperoxy) hexane (trade name "Perhexa 25B", manufactured by NOF CORPORATION), and hexyltrimethoxysilane (trade name "KBM306" as a saturated silane compound.
3 ", manufactured by Shin-Etsu Chemical Co., Ltd.) at a rate of 0.5 part, and uniformly stirred and mixed to prepare a silane solution.

( 2) Manufacture of silane-modified polyolefin Self-wiping type meshing type equipped with a screw (diameter 47 mm, L / D = 35) composed of a double-threaded screw element and a kneading disc element, and a cylinder barrel of 10 divisions A coat hanger die having a sheet-like discharge shape having a width of 200 mm and a thickness of 5 mm was connected to the tip of a co-rotating twin-screw extruder (model “TEX-44”, manufactured by Japan Steel Works). The above 1
The cylinder barrel of 0 division is installed from the first barrel to the tenth barrel from the upstream side to the downstream side of the extruder,
The temperature of each barrel and coat hanger die is 170 ° C for the first to sixth barrels, 155 ° C for the seventh barrel,
Eighth barrel to tenth barrel and one coat hanger die
It was set at 40 ° C.

Linear low-density polyethylene (trade name "Rinirex AR4910", manufactured by Nippon Petrochemical Co., Ltd.) was charged into the hopper, and 20 k was obtained using a screw feeder.
The extruder was fed through the feed port at a feeding rate of g / hour.
At the same time, a micro pump (model “VC-102 MOD
EL186-346 ", manufactured by Chuo Science Co., Ltd.), the silane solution obtained above was supplied to the extruder through the same supply port at a supply rate of 316 g / hour. Further, di-n-butyltin dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a silanol condensation catalyst at a feed rate of 8 g / hour using a plunger pump, and was extruded from a ninth barrel through a press-fitting nozzle from a ninth barrel. Supplied to. During this period, the extruder was operated at a screw rotation speed of 40 rpm and discharged from the coat hanger die discharge port to obtain silane-modified polyethylene.

( 3) Evaluation The appearance, surface smoothness, and gel fraction of the silane-modified polyethylene obtained above were evaluated by the following methods. The results were as shown in Table 1.

Appearance / Surface Smoothness The appearance / surface smoothness of the obtained silane-modified polyethylene was visually observed, and the appearance / surface smoothness was evaluated according to the following criteria. [Criteria] ◎ ・ ・ ・ Appearance / Surface smoothness: Excellent ○ ・ ・ ・ Appearance / Surface smoothness: Good △ ‥‥ Appearance / Surface smoothness: Yes × ‥ Appearance / Surface smoothness: Not good

Gel Fraction The obtained silane-modified polyethylene was placed in an autoclave and subjected to hot water treatment at 110 ° C. for 2 hours to prepare crosslinked polyethylene. Next, the obtained crosslinked polyethylene was immersed in hot xylene at 130 ° C. for 2 days, insolubles were taken out and vacuum dried, and the gel fraction (wt%) was calculated by the following formula.

(Examples 2 and 3 and Comparative Examples 1 to 3)

Five kinds of silane solutions were prepared in the same manner as in Example 1 except that the silane solution had the composition shown in Table 1.

Then, Example 1 was repeated except that the five kinds of silane solutions obtained above were used and the supply amounts shown in Table 1 were used.
Five kinds of silane-modified polyethylene were obtained in the same manner as in.

Table 5 shows the results of evaluation of the appearance, surface smoothness, and gel fraction of the five types of silane-modified polyethylene obtained above in the same manner as in Example 1.

[0058]

[Table 1]

[0059]

As described above, according to the production method of the present invention, it is possible to obtain a silane-modified polyolefin which has a high gel fraction and is excellent in various characteristics and which is excellent in appearance and surface smoothness due to the suppression of scorch phenomenon. It can be easily obtained.

[0060]

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an extruder used in the present invention.

[Explanation of symbols]

 1 2 screw extruder 2 supply port 3 screw feeder with hopper 4 silane solution tank 5 chemical micro pump 6 silanol condensation catalyst tank 7 plunger pump 8 die a grafting reaction zone b catalyst kneading zone

Claims (1)

[Claims] 1. A polyolefin, an olefinically unsaturated silane compound represented by the following general formula (1), a free radical generator, a silanol condensation catalyst, and the following general formula (2) per 100 parts by weight of the polyolefin. A method for producing a silane-modified polyolefin, which comprises heating and mixing a composition containing 0.01 to 5 parts by weight of a saturated silane compound in an extruder to cause a reaction. Embedded image (In the formula, R ¹ represents a monovalent olefinically unsaturated hydrocarbon group or a monovalent olefinically unsaturated hydrocarbonoxy group, Y represents a hydrolyzable organic group, and R ² represents a group Y or hydrogen. Group or a saturated aliphatic hydrocarbon group) (In the formula, R ³ represents a linear or branched saturated hydrocarbon group having 1 to 30 carbon atoms, Y represents an organic group capable of being hydrolyzed, and R ⁴ is a group Y or a hydrogen group or 1 to 1 carbon atoms. Represents 30 linear or branched saturated hydrocarbon groups)