JPS62135505A - Ethylene copolymer capable of silane crosslinking - Google Patents

Abstract

PURPOSE:To obtain the titled copolymer excellent in storage stability, moldability and crosslinkability, by specifying the unsaturated silane compound content, MW distribution, density, chlorine content, etc., of a copolymer obtained by copolymerizing ethylene with an unsaturated silane compound. CONSTITUTION:An unsaturated silane compound such as gamma-(meth) acryloxypropyltrimethoxysilane is mixed with ethylene, a radical generator and 0.5-15wt% chain transfer agent (e.g., methane), and the obtained mixture is polymerized at 170-250 deg.C and a pressure of 1,500-3,000kg/cm<2> to obtain a silane-crosslinkable ethylene copolymer of an unsaturated silane compound content of 0.2-5wt%, a MW distribution <=10, a melt flow rate of 0.1-10g/10min, a density <=0.932g/cm<3> and a chlorine content, a methacrylic acid content and an acrylic acid content <=0.2ppm (by weight), respectively.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a storage-stable four-component copolymer that can be crosslinked with silane by water and has excellent processability and crosslinking properties, The present invention relates to an ethylene copolymer suitable for various molded object fields such as coatings and containers.

[Prior art]

It is common practice to crosslink ethylene polymers to improve their physical properties and use them for various purposes.

Cross-linking of ethylene polymers has mainly been carried out using organic peroxides or radiation irradiation, but these methods have problems in terms of safety, require expensive equipment, and have little freedom in the shape of molded products. There are drawbacks. Therefore, in recent years, a method of silane crosslinking by bringing a copolymer of ethylene and an unsaturated silane compound into contact with moisture in the presence of a silanol condensation catalyst has been attempted, as it offers inexpensive equipment and a high degree of freedom in the shape of molded products. (Japanese Unexamined Patent Publication No. 55-9611).

[Problem that the invention seeks to solve]

However, this silane crosslinking method has the disadvantage that the storage stability of the ethylene-unsaturated silane compound copolymer before crosslinking, the moldability, the tensile properties of the crosslinked molded product, etc. are not necessarily satisfactory.

The present invention was made based on the discovery that only an ethylene-unsaturated silane compound copolymer having a specific molecular structure and containing few impurities can be subjected to the silane crosslinking method without these drawbacks.

Means for Solving the 3 Problems] That is, the present invention provides an unsaturated silane compound of γ-methacryloxypropyltrimethoxysilane or γ-acryloxypropyltrimexysilane alone or in a composite system with a concentration of 0.2 to Contains 5%, has a molecular weight distribution of 10 or less, a melt flow rate of 0.1 to 10g/10 min, and a density of 0.
932 g/crA or less, and the chlorine content and methacrylic acid and acrylic acid content are each 0.2 double fflpp
silane-crosslinkable ethylene copolymer, characterized in that it essentially consists of ethylene and the unsaturated silane compound having a molecular weight of less than m.

[For production]

The ethylene copolymer of the present invention essentially consists of ethylene and the above-mentioned specific unsaturated silane compound. Here, "woody" refers to other unsaturated monomers, such as α-olefins such as propylene, butene-1,4-methylpentene-1, and hexene-1; vinyl such as vinyl acetate and vinyl butyrate. Esters; unsaturated organic acid derivatives such as methyl acrylate, methacrylamide, methyl methacrylate, acrylonitrile, maleic anhydride;
Unsaturated aromatic fluorophores such as styrene and α-methylstyrene: vinyl ethers such as vinyl methyl ether, etc. are grafted, randomly or Copolymers containing in block form, vinyltrimethoxysilane,
A copolymer containing an unsaturated silane compound other than the specific unsaturated silane compound such as vinyltriethoxysilane in an amount smaller than the content of the specific unsaturated silane compound also falls under the copolymer referred to herein. means.

Copolymers consisting essentially of unsaturated silane compounds other than those mentioned above and ethylene are less effective in the present invention.

The ethylene copolymer of the present invention contains an unsaturated silane compound of γ-methacryloxypropyltrimethoxysilane or γ-acryloxypropyltrimethoxysilane alone or in a composite system in an amount of 0.2 to 5% by weight, preferably 0.
Contains 5 to 3% by weight, has a molecular weight distribution (ratio of weight average molecular weight to number average molecular weight) of 10 or less, preferably 8 or less, and has a melt flow rate (VFR) of 0.1 to log/10 minutes.
Preferably 0.3 to 5 g/10 min, density 0.932
g/ctA or less, preferably 7 or 0.930 g/Cn (
or less, and the chlorine content and the methacrylic acid and acrylic acid contents are each not more than 0.2 ppm by weight, preferably 0.
It is an ethylene copolymer consisting essentially of 1 ppm by weight or less of ethylene and the unsaturated silane compound.

Here, if the unsaturated silane compound is less than 0.2% by weight, a sufficient degree of crosslinking cannot be obtained, while if it exceeds 5% by weight, the storage stability, moldability and tensile properties of the crosslinked molded product will deteriorate. When the molecular weight distribution exceeds IO, storage stability and molding processability deteriorate, and the tensile properties of the crosslinked molded product also become insufficient. Furthermore, if the MFR is less than 0.1 g/10 minutes, the molding processability and tensile properties of the crosslinked molded product will be insufficient;
If it exceeds 10 g/10 minutes, the tensile properties of the crosslinked molded product will become unsatisfactory.

The density of this copolymer is generally 0.920 g/ca or more, but if it exceeds 0.932 g/crA, the crosslinking properties become poor.

Furthermore, either the chlorine content or the methacrylic acid and acrylic acid content in this copolymer is 0.2 fold fflp.
pm B filtration deteriorates the storage stability, molding processability, and tensile properties of the crosslinked molded product. These impurities are introduced by unsaturated silane compounds as raw materials.

Such an ethylene copolymer of the present invention can be used, for example, at a pressure of 1000 to 4000 kg/ct and a temperature of 150 to 28 kg/ct.
It is obtained by copolymerizing ethylene with the above unsaturated silane compound and optionally other unsaturated monomers in the presence of a radical generator and a chain transfer agent at 0°C.

The reactor may be either a tank type or a front type, but the tank type is more reasonable and preferable.

Specifically, in order to obtain a molecular weight distribution of 10 or less, a chain transfer agent is used, and the polymerization pressure is preferably 500 to 500 m/month.
3000 kg/co! And the pressure is 1500kg/c
The reaction temperature at f is 210°C or less and the pressure is 3000
The polymerization occurs at a reaction temperature of 250°C or less when the reaction temperature is 250°C or less.

In addition, in order to obtain an MFR of 0.1 to 10 g/10 minutes, the amount of chain transfer agent should be relatively large, for example, 0.5 to 15% by weight relative to the total amount of polymerization monomer and chain transfer agent. % binding, polymerization pressure and reaction temperature are variously controlled.

The preferred conditions for obtaining a product with a density of 0.937 g/c++ or less are a polymerization pressure of 1500 to 3000 kg/c++.
c+d, the reaction temperature at a pressure of 1500 kg/cd is 170°C or higher, and the reaction temperature at a pressure of 3000 kg/c++1 is 190°C or higher, and more preferably a chain transfer agent such as propylene or butene is used. It is effective to use α-olefins, especially propylene.

Therefore, to summarize these, the preferred polymerization conditions for obtaining the ethylene copolymer of the present invention are that the polymerization pressure is 150
0-3000kg/crA and reaction temperature 170-2
50°C and using a specific amount of chain transfer agent.

Furthermore, in order to obtain a product in which the chlorine content and the methacrylic acid and acrylic acid contents are each 0.2 ppm or less, the chlorine content and the methacrylic acid and acrylic acid contents in the unsaturated silane compound to be used must each be 60 ppm or less.
pm or less, preferably 30 ppm or less by weight.

The radical generator used for polymerization under the above conditions is:
Organic peroxides (e.g. lauroyl peroxide, dibropionyl peroxide, hensyl peroxide, di-butyl peroxide, t-butyl hydroperoxide, t-butyl peroxypivalate, [-butyl peroxyiso butyrate, etc.), molecular oxygen, ab compounds (for example, abbisisobutyronitrile, etc.), etc. can be used. Chain transfer agents include paraffinic hydrocarbons (e.g., methane, hexane, etc.), α-olefins (e.g., propylene, butene, etc.), ketones (e.g., acetone, cyclohexanone, etc.), aldehydes (e.g., acetaldehyde, n- butyraldehyde, etc.),
Aromatic hydrocarbons and the like can be used. The copolymerizable unsaturated monomer means the unsaturated monomer mentioned above in the explanation of "essential".

The copolymer of the present invention is applied to, for example, crosslinked foams, crosslinked films, crosslinked wire covering materials, pipes, tubes, and the like.

Silanol condensation catalysts used for crosslinking in applications include, for example, dibutyltin dilaurate, stannous acetate,
Tin-octoate, lead naphthenate, zinc caprylate, 2
- metal carboxylates such as iron ethylhexanoate, cobalt naphthenate, organometallic compounds such as titanate esters and chelate compounds (e.g. tetrabutyl titanate, tetranonyl titanate and bis(acetylacetonitrile) di-isopropyl titanate, etc.)
, other bases and acids. Among these, organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin diacetate are preferred.

〔Example〕

The physical properties and quality of the ethylene copolymers produced in the following examples were evaluated by the following methods.

(Evaluation of the physical properties) (1) Content of unsaturated silane compound By infrared spectrophotometer.

(2) Molecular weight distribution The weight average molecular weight (MW) and number average molecular weight (Mn) are measured by quantifying the fractionated product by gel diffusion chromatography (GPC) using a low-angle laser light scattering device, and using the following formula and method. I asked for it.

The calibration curve is based on standard high-density polyethylene NBS-3R.
It was made using NB5-3R.

(Weight average molecular weight) = Δ■・Σ(K/R)−'/m Here, ΔV is the sampling volume = 2π2n2/(λ' N)(dn/dc)2(Hc
os2 θ)n: refractive index λ: wavelength N: Avogadro's number dn/dc: index increment of refractive index θ: scattering angle R is 2 volumes't (difference between the Rayleigh ratio of l and n volume m
is the injected polymer weight t (number average molecular star) is E, E, Droh and R98,
Calculations were made based on Mendel-son's method.

(31VFR According to JIS-676 (l).

(4) Density According to JIS-6760.

(5) Content of methacrylic acid and acrylic acid (a) 1
10g of copolymer was immersed in 0mf acetone and heated at 50°.
Extraction is carried out for 24 hours at C.

(o) Perform coumarin fluorescence derivatization for 2 hours at 50°C.

(c) Fluorescent extraction using liquid chromatography.

(6) Chlorine content (a) The copolymer is immersed in a methanol/acetone mixed solvent and heated at 50° C. for 24 hours, and then the solvent is separated from the copolymer.

(D) Add a methanol solution of sodium methylate to this container and mix well.

(c) Add a bromophenol blue indicator to this solution, and drop nitric acid until the indicator turns yellow.

(iv) Then, insert the electrode of an automatic potentiometric titrator and titrate with a silver nitrate solution while stirring.

(7) Storage stability M of ethylene-unsaturated silane compound copolymer immediately after production
The ratio of FR to VFR of the copolymer stored for one month in an atmosphere of 23° C. and 50% relative humidity was determined, and the rate of decrease was evaluated as follows.

A: Less than 10% B: 10 to 30% C: More than 30% (8) Moldability Low density polyethylene containing 1% by weight of dibutyltin dilaurate based on 100 parts by weight of the ethylene-unsaturated silane compound copolymer (Mitsubishi “Yukalon EH30J” manufactured by Yukasha
) was blended and extruded into a strand through an orifice with an inner diameter of 21 at 170° C. using an extruder with L/D 22, and its appearance was observed.

! 9) Crosslinking properties A sample (former) in which a strand extruded using the moldability evaluation method described above was crosslinked by immersing it in 80°C hot water for 8 hours, and the same strand was placed in an atmosphere of 23°C and 150% relative humidity. 1 g of each sample was taken from the sample (the latter) which had been left for a week to undergo cross-linking treatment, placed in a Soxhlet extractor, and extracted with boiling xylene for 10 hours to determine the gel fraction of each sample. The ratio of the latter gel fraction to the gel fraction was evaluated as follows.

A: More than 80% B: 50 to 80% C: Less than 50% (10) Tensile properties The 8-hour immersed crosslinked strand obtained by the above method for evaluating crosslinking properties was tensile-stretched at 200% using an autograph.
Tensile elongation was measured in m1/min and evaluated as follows.

A: More than 350% B: 250 to 350% C: Less than 250% Examples and Comparative Examples In a reactor equipped with a stirrer and having an internal volume of 1.5 liters, ethylene, the unsaturated silane compounds shown in Table 1, and the molecular weight regulator were added. The mixture and the radical generator shown in Dotomo were supplied as a catalyst to continuously produce an ethylene copolymer.

The polymerization conditions at this time and the physical properties and quality evaluation of the produced copolymer were as shown in Table 1.

The meanings of the abbreviations in Table 1 are as follows.

flr M: γ-methacryloxypropyltrimethoxysilane (21r-A: r-acryloxypropyltrimethoxysilane!3) l B: t-butylperoxyisobutyrate! 41.1: t-butyl peroxyisopropyl carbonate f5) PV: t-butyl peroxyisopropyl carbonate (61P
: Propylene f7) H + hequinane (blank below)

Claims (1)

[Claims] 0.2 to 5% by weight of an unsaturated silane compound such as γ-methacryloxypropyltrimethoxysilane or γ-acryloxypropyltrimethoxysilane alone or in a composite system
Contains, molecular weight distribution is 10 or less, melt flow rate is 0.1 to 10 g/10 min, density is 0.932 g/cm^
A silane-crosslinkable ethylene copolymer essentially consisting of ethylene and the unsaturated silane compound, and having a chlorine content and a methacrylic acid content and an acrylic acid content of 0.2 ppm by weight or less, respectively. .