JP2007308541A - Manufacturing process of crosslinked polyolefin and slightly crosslinked ethylene-vinyl acetate copolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process of a crosslinked polyolefin which allows an easy handling of the organic peroxide and produces a crosslinked polyolefin with a small amount of the gel portion and a slightly crosslinked ethylene-vinyl acetate copolymer manufactured by this process. <P>SOLUTION: This manufacturing process of the crosslinked polyolefin comprises manufacturing the crosslinked polyolefin by crosslinking a crosslinkable polyolefinic resin with an organic peroxide and comprises adding an organic peroxide to a base resin with an MFR ≥0.4 time that of the crosslinkable polyolefinic resin to prepare a master batch, adding the obtained master batch to the crosslinkable polyolefinic resin and melt-kneading the mixture. The slightly crosslinked ethylene-vinyl acetate copolymer thus manufactured has an MFR of 0.01-5 g/10 minutes and an Mw/Mn of 2-12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a crosslinked polyolefin and a slightly crosslinked ethylene-vinyl acetate copolymer.

  The olefin resin is required to have a high molecular weight (low MFR) depending on the application. Conventionally, as a method for obtaining a low MFR olefin resin, a method of crosslinking an olefin resin with a liquid or an organic peroxide dissolved in a solvent is known. However, organic peroxides used here are classified as dangerous goods under the Fire Service Law, and therefore, care must be taken when handling them. For this reason, when an olefin resin is cross-linked with an organic peroxide, a method is employed in which the organic peroxide is blended with the resin and used as a resin composition containing the organic oxide in a high concentration. There is. Moreover, when an olefin-based resin is crosslinked, a gel is generated, and the quality may be deteriorated when used for the appearance quality of a molded product and the use for dissolving an organic solvent.

  As a result of studying a crosslinking method in which gel is not easily generated when an olefin-based resin is crosslinked using an organic peroxide that has been masterbatched, the present inventor has found that the MFR of the base resin used in the masterbatch and the olefin to be crosslinked It has been found that when the MFR of the resin is in a specific relationship, the gel formation is reduced, and the present invention has been completed.

In addition, Patent Document 1 discloses a method for producing a slightly crosslinkable ethylene-vinyl acetate copolymer with less gel. In this invention, by using an ethylene-vinyl acetate copolymer having specific physical properties. The problem is solved.
JP 2003-171421 A

An object of the present invention is to provide a method for producing a crosslinked polyolefin, in which an organic peroxide can be easily handled and gel formation is small.
Another object of the present invention is to provide a microcrosslinked ethylene-vinyl acetate copolymer having a low gel content in the copolymer.

  The method for producing a crosslinked polyolefin according to the present invention is a method for producing a crosslinked polyolefin by crosslinking the crosslinkable olefin resin (A) with an organic peroxide, the melt flow rate (JIS K7210-1999; 190 ° C.). 2. Under a load of 2.16 kg, blended with a resin (B) having a melt flow rate of 0.4 times or more of the crosslinkable olefin resin (A), a high concentration organic peroxide resin (hereinafter referred to as a master batch) The organic peroxide high-concentration resin obtained is added to a cross-linkable olefin resin and melt-kneaded. In the present invention, the organic peroxide high-concentration resin (masterbatch) is a high concentration of organic peroxide (specifically, 0.1 to 20 parts by weight of organic peroxide per 100 parts by weight of resin (B)). It means a resin composition contained in a ratio).

  The resin B (hereinafter sometimes referred to as “masterbatch resin”) is preferably an olefin resin having an MFR of 10 g / 10 min or more, and the crosslinkable olefin resin is a polyethylene or ethylene-vinyl ester copolymer. It is preferable that

  The crosslinkable olefin resin is preferably an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 15 to 60% by weight, and the base resin has a vinyl acetate unit content of 25 to 50% by weight, An ethylene-vinyl acetate copolymer having an MFR of 10 g / 10 min or more is preferred.

  The micro-crosslinked ethylene-vinyl acetate copolymer according to the present invention is produced by the above-described method using an ethylene-vinyl acetate copolymer as a masterbatch resin and a crosslinkable olefin resin, and the vinyl acetate unit content is 15 to 60 wt. %, MFR is 0.01 to 5 g / 10 min, and molecular weight distribution measured by gel permeation chromatography (GPC) (Mw / Mn, polystyrene conversion, Mw: weight average molecular weight, Mn: number average molecular weight) Is 2-12.

According to the method for producing a crosslinked polyolefin of the present invention, it is easy to handle an organic peroxide, and a crosslinked polyolefin having a low gel content can be obtained.
The finely crosslinked ethylene-vinyl acetate copolymer of the present invention has a low gel content in the copolymer.

Hereinafter, the method for producing a crosslinked polyolefin and the slightly crosslinked ethylene-vinyl acetate copolymer according to the present invention will be specifically described.
[Crosslinkable olefin resin]
Examples of the crosslinkable olefin resin used in the present invention (olefin resin used for crosslinking) include ethylene polymers such as polyethylene and ethylene-vinyl ester copolymers.

  Polyethylene is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin, and the structural unit derived from ethylene is 55 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more. It is desirable that the structural unit derived from the α-olefin is present in a proportion of 45 mol% or less, preferably 30 mol% or less, more preferably 10 mol%.

Polyethylene has an MFR of 5 to 1000 g / 10 min, preferably 5 to 500 g / 10 min, more preferably 5 to 200 g / 10 min, and a density of usually 890 to 990 g / cm ³ , preferably 890 to 980 g / cm. ^{3 is} more preferably 900 to 980 g / cm ³ .

  Examples of the α-olefin used in producing the polyethylene include α-olefins having 3 to 20 carbon atoms, and specifically, propylene, 1-butene, 1-hexene, 4-methyl-1 -Pentene, 1-octene, 1-decene, 1-tetradecene, 1-octadecene and the like are used, and these α-olefins can be used alone or in combination of two or more.

  Specific examples of polyethylene include ethylene homopolymer, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 4-methyl-1-pentene copolymer, ethylene / 1-hexene copolymer. Examples include coalescence.

The ethylene-vinyl ester copolymer has a constituent unit content derived from ethylene (ethylene unit content) of 85 to 40% by weight, preferably 65 to 40% by weight, more preferably 65 to 45% by weight. The content of the structural unit derived from the ester (vinyl ester unit content) is 15 to 60% by weight, preferably 35 to 60% by weight, more preferably 35 to 55% by weight. When cross-linking an ethylene-vinyl ester copolymer having a vinyl ester unit content of the ethylene-vinyl ester copolymer within the above range, an organic peroxide dissolved in a liquid or a solvent is directly added. In the method for producing a crosslinked polyolefin, which will be described later, the ethylene-vinyl ester copolymer (pellet) is dissolved and fused by an organic peroxide, and uniform crosslinking may be difficult. Addition of peroxide is improved. In the present invention, in order to prevent pellet blocking, if necessary, a known slip agent is blended in advance with an ethylene / vinyl ester copolymer, or a known antiblocking agent coat is applied to the surface of the copolymer pellet. Can do.

The ethylene-vinyl ester copolymer has an MFR of 5 to 1000 g / 10 minutes, preferably 10 to 700 g / 10 minutes, and more preferably 10 to 500 g / 10 minutes.
Specific examples of the vinyl ester component copolymerizable with ethylene in the ethylene-vinyl ester copolymer include vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl persate, vinyl laurate, vinyl stearate, Examples include vinyl benzoate, vinyl salicylate, and vinyl cyclohexanecarboxylate.

  Specific examples of the ethylene-vinyl ester copolymer include an ethylene-vinyl acetate copolymer (EVA), an ethylene-vinyl propionate copolymer, an ethylene-n-vinyl butyrate copolymer, and an ethylene-persamic acid. Vinyl copolymer, ethylene-vinyl laurate copolymer, ethylene-vinyl stearate copolymer, ethylene-vinyl benzoate copolymer, ethylene-vinyl salicylate copolymer, ethylene-vinyl cyclohexanecarboxylate copolymer, etc. Is mentioned.

[Resin B (resin for masterbatch)]
Examples of the masterbatch resin used in the present invention include ethylene polymers such as the above-described polyethylene and ethylene-vinyl ester copolymers.

However, the master batch resin has an MFR (based on JIS K7210-1999, 190 ° C., 2160 g load) of 10 g / 10 min or more, preferably 10 to 1000 g / 10 min, and more preferably 10 to 500 g / 10 min. When the MFR of the base resin is in the above range, the dispersibility of the organic peroxide of the melt-kneaded body in the method for producing a crosslinked polyolefin described later is good.

  As the masterbatch resin, it is preferable to use a resin having a combination of monomers similar to the crosslinkable olefin resin. For example, when the crosslinkable olefin resin is an ethylene / propylene copolymer, an ethylene / propylene copolymer is used as the base resin, and when the crosslinkable olefin resin is an ethylene-vinyl acetate copolymer, the base is used. An ethylene-vinyl acetate copolymer is used as the resin.

  When an ethylene-vinyl acetate copolymer is used as the resin for the master batch, the constituent unit content derived from vinyl acetate is 10 to 50% by weight, preferably 15 to 45% by weight, and the MFR is 10 g / 10 minutes. As mentioned above, it is preferable to use the copolymer which is preferably 10 to 1000 g / 10 min.

[Organic peroxide]
Examples of the organic peroxide used in the present invention include cyclohexanone peroxide, di (t-butyl) peroxide, dicumyl peroxide, t-butylcumyl peroxide, diacyl peroxide, didecanoyl peroxide, benzoyl peroxide, and m-toluyl peroxide. 2,4-dichlorobenzoyl peroxide, 1,1-di (t-butylperoxy) cyclohexane, 1,1-di (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5 -Di (t-butylperoxy) hexane, 1,3
-Di (t-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, n-butyl-4,4-bis (t-butylperoxy) valerate, t-butylperoxyacetate, t -Butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate, di ( t-Butylperoxy) isophthalate, t-butylperoxymalate, methyl ethyl ketone peroxide and the like.

[Other ingredients]
In the present invention, if necessary, fillers such as talc, calcium carbonate, clay, mica, barium sulfate, magnesium hydroxide, aluminum hydroxide, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, triaryl. Polyfunctional monomers such as allyl isocyanurate, polyfunctional polymers such as 1,2-polybutadiene, crosslinking aids such as sulfur compounds, antioxidants, lubricants, pigments, dyes, weathering agents, antiblocking agents, various stabilizers Plasticizers, oils, foaming agents, flame retardants and the like can be used.

〔Master Badge〕
The organic peroxide high-concentration resin (masterbatch) used in the present invention contains the above masterbatch resin and the above organic peroxide, and the organic peroxide is added in an amount of 0.000 by weight relative to 100 parts by weight of the resin (B). 1 to 20 parts by weight, preferably 0.1 to 15 parts by weight, more preferably 0.1 to 10 parts by weight.

As a method for producing a masterbatch, a conventionally known method is adopted. For example, a base resin and an organic peroxide are mixed with a Banbury mixer, a Henschel mixer, or a kneader in a nitrogen atmosphere, or at a low temperature, uniaxially. It can be produced by melt-kneading with an extruder or a twin screw extruder.
In the present invention, the organic peroxide can be either a liquid peroxide at room temperature or a solid peroxide at room temperature, but if a solid peroxide is used at room temperature, the organic peroxide is dissolved in a solvent. And preferably used.

[Method for producing crosslinked polyolefin]
In the method for producing a cross-linked polyolefin of the present invention, the cross-linkable olefin resin, the master batch, and other compounding agents as necessary are kneader, Henschel mixer, Banbury mixer, single screw extruder, twin screw extruder. Mix using the machine. Specifically, for example, after the crosslinkable olefin resin and the master batch are dry blended, they are put into a hopper of a twin screw extruder set at 80 to 200 ° C. Before the organic peroxide is decomposed, it is sufficiently dispersed in the crosslinkable olefin resin and then subjected to a crosslinking reaction.

  The MFR of the masterbatch resin used at this time is 0.4 times or more, preferably 0.5 times or more, more preferably 0.5 to 200 times the MFR of the crosslinkable olefin resin (A). When the MFR of the masterbatch resin and the MFR of the crosslinkable olefin resin are in the above relationship, the obtained crosslinked polyolefin has a small gel content.

[Crosslinked polyolefin]
The crosslinked polyolefin produced by the method as described above usually has a gel content of 30 mg / 20 g or less, preferably 20 mg / 20 g or less, more preferably 10 mg / 20 g or less.

The gel content of the crosslinked polyolefin is measured as follows.
(Method for measuring gel content)
(1) At room temperature, 20 ± 0.1 g of a sample dried by blowing industrial air for about 24 hours is placed in 150 ml of toluene at 30 ± 3 ° C. and left for 48 hours to dissolve the sample.
(2) The dissolved material is filtered through a 200-mesh wire mesh to extract undissolved material (gel).
(3) Weigh the wire mesh to which the undissolved material (gel) is attached, and obtain the gel content from the following formula.

Gel content (mg / 20 g) = (weight of wire mesh after filtration (g) −weight of wire mesh (g)) × 1000/20
The crosslinked polyolefin produced by the method as described above has an MFR of 0.01 to 5 g / 10 min, preferably 0.1 to 5 g / 10 min, more preferably 0.1 to 4 g / 10 min. The molecular weight distribution (Mw / Mn, polystyrene conversion, Mw: weight average molecular weight, Mn: number average molecular weight) measured by gel permeation chromatography (GPC) is preferably 2-12, Is preferably in the range of 2-11, more preferably 2-10.

  A preferred embodiment of the crosslinked polyolefin is a slightly crosslinked ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 15 to 60% by weight and MFR and Mw / Mn within the above ranges.

Such a cross-linked polyolefin is suitable for use in which it is dissolved in an organic solvent, for example, an adhesive use. When used as an adhesive, if the gel content is large, the filter is likely to be clogged, and the adhesive having a large gel content tends to cause poor adhesion. This crosslinked polyolefin is suitable for applications in which problems occur when the gel content is large.
[Example]
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

The components used in Examples and Comparative Examples are as follows.
Ingredient (A)
Ethylene-vinyl acetate copolymer Vinyl acetate unit content = 42% by weight
MFR (JIS K7210-1999, 190 ° C, 2160 g load) = 65 g / 10 min
Ingredient (B)
Ethylene-vinyl acetate copolymer Vinyl acetate unit content = 33% by weight
MFR (JIS K7210-1999, 190 ° C, 2160 g load) = 0.2 g / 10 min
Ingredient (C)
Ethylene-vinyl acetate copolymer Vinyl acetate unit content = 33% by weight
MFR (JIS K7210-1999, 190 ° C, 2160 g load) = 14 g / 10 min
Ingredient (D)
Ethylene-vinyl acetate copolymer Vinyl acetate unit content = 33% by weight
MFR (JIS K7210-1999, 190 ° C, 2160 g load) = 31 g / 10 min
Ingredient (E)
Ethylene-vinyl acetate copolymer Vinyl acetate unit content = 28 wt%
MFR (JIS K7210-1999, 190 ° C, 2160 g load) = 400 g / 10 min
Ingredient (F)
Product name: Perbutyl E
T-Butylperoxy-2-ethylhexyl monocarbonate manufactured by Nippon Oil & Fat Co., Ltd. [Examples, Comparative Examples]
Preparation of masterbatch The above components (B) to (E) and component (F) were supplied to a Henschel mixer in the proportions shown in Table 1, mixed for 30 seconds, and then left at 23 ° C. for 24 hours to obtain a masterbatch. (1) to (4) were obtained.

Manufacture of cross-linked polyolefin Master batches (1) to (4) are blended in proportions shown in Table 2 to the anti-blocking component (A) (cross-linkable olefin resin), and this is mixed with a 40 mmφ single unit equipped with a pelletizer. It is fed to a shaft extruder [manufactured by Nakatani Machinery Co., Ltd., product number: VSX 40 m / m], melt kneaded and granulated under the following extrusion conditions (or melt kneading conditions), and the component (A) is partially (or A highly) crosslinked polyolefin was obtained.
Melt flow rate The melt flow rate (MFR) of the crosslinked polyolefin was measured according to JIS K7210-1999 at 190 ° C. and a load of 2160 g.
Extruder Conditions Extrusion conditions in the single screw extruder are as follows.

L / D = 28
Barrel temperature (° C.): C1 = 80, C2 = 150, C3 = 160,
C4 = 160, A = 160, D = 160
Screw rotation speed: 40rpm
Extrusion rate: 8kg / h
Residence time: 80 seconds The gel content and MFR of the obtained crosslinked polyolefin were evaluated according to the above methods. The results are shown in Table 2. The relationship between the MFR of the base resin of the master batch and the gel content of the crosslinked polyolefin is shown in FIG. The gel content was expressed logarithmically.

As shown in FIG. 1, the MFR of the base resin of the masterbatch has an inflection point of the gel of the cross-linked polyolefin around 0.4 times the MFR of the polyolefin to be cross-linked, and the MFR of the base resin of the master batch is When the MFR of the polyolefin resin to be crosslinked is about 0.4 times or more, the gel content is stabilized at a low level. From this figure, even when the MFR value of the base resin of the star batch exceeds the MFR of the example, it is easily expected that the gel content is low. In the above examples and comparative examples, the MFR of the polyolefin to be crosslinked is 65 g / 10 min. However, even if the MFR of the polyolefin to be crosslinked is larger or smaller than this value, the base of the masterbatch It is expected that the relationship between the MFR of the resin and the gel content of the crosslinked polyolefin will be the same as that shown in FIG.

It is a figure which shows the relationship of MFR of the base resin (resin for masterbatch) of a masterbatch, and the gel part of the crosslinked polyolefin.

Claims (6)

A method for producing a crosslinked polyolefin by crosslinking a crosslinkable olefin resin (A) with an organic peroxide, wherein the organic peroxide is converted into its melt flow rate (JIS K7210-19).
99; 190 ° C., under 2.16 kg load) is blended with resin (B) having a melt flow rate of 0.4 times or more of the crosslinkable olefin resin (A) to produce a high concentration organic peroxide resin. A method for producing a crosslinked polyolefin, comprising adding the obtained organic peroxide high-concentration resin to a crosslinkable olefin resin and melt-kneading. The resin (B) is melt flow rate (JIS K7210-1999; 190 ° C.,
The method for producing a crosslinked polyolefin according to claim 1, wherein the olefin resin is under a load of 2.16 kg (10 g / 10 min).   The method for producing a crosslinked polyolefin according to claim 1, wherein the crosslinkable olefin resin is polyethylene or an ethylene-vinyl ester copolymer.   The method for producing a crosslinked polyolefin according to claim 1 or 2, wherein the crosslinkable olefin resin is an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 15 to 60% by weight.   The resin (B) is an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 10 to 50% by weight and a melt flow rate (JIS K7210-1999; 190 ° C., under 2.16 kg load) of 10 g / 10 min or more. The method for producing a crosslinked polyolefin according to claim 1 or 2. And an ethylene-vinyl acetate copolymer as the crosslinkable olefin resin, the vinyl acetate unit content produced by the method according to claim 1 or 2 is 15 to 60% by weight, and a melt flow rate (JIS K7210- 1999; 190 ° C., under 2.16 kg load) is 0.01 to 5 g / 10 min, molecular weight distribution measured by gel permeation chromatography (GPC) (Mw / Mn, polystyrene conversion, Mw: weight average molecular weight, A finely crosslinked ethylene-vinyl acetate copolymer having a Mn: number average molecular weight of 2 to 12.

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