JPH03199417A - Naturally degradative monofilament - Google Patents

Abstract

PURPOSE:To provide the subject product composed of a specified ratio of a specified modified PE, polycaprolactone and a high-density PE, satisfying specified physical properties, excellent in strength elongation characteristics, having natural degradation properties, capable of prevention of environmental pollution and suitable for a fish net, a fishing line, an agricultural material, etc. CONSTITUTION:An objective monofilament composed of 20-50wt.% modified PE obtained by copolymerization between ethylene as the main constituent and 1.5-7.0wt.% carbon monoxide or between another ethylenically unsaturated compound (preferably vinyl acetate or ethyl acrylate) and that, 3-20wt.% polycaprolactone (preferably obtained by ring opening polymerization of epsilon- caprolactone and having 60 deg.C melting point and 20000-50000 molecular weight) and 20-77wt.% high-density PE and having >=3g/d tensile strength, >=2g/d knot strength and >=5% breaking strength.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polyethylene-based self-disintegrating monofilament.

(Prior Art) Conventionally, as monofilaments for industrial materials used in fishing nets, fishing lines, agricultural nets, etc., monofilaments mainly made of polyamide, polyester, vinylon, polyolefin, etc. have been used. Therefore, these monofilaments do not have self-decomposition properties, and if they are left in the sea, mountains or fields after use, they cause various types of pollution. This problem can be solved by incinerating, burying, or collecting and recycling after use, but these treatments require a lot of money, so in reality, they are left abandoned in the sea, mountains, and fields.
Situations often occur in which they become entangled with birds, marine animals, and diapers, killing or injuring them, or become entangled with ships' propellers, causing ship accidents.

One possible way to solve these problems is to use materials that naturally decompose or disintegrate when exposed to light or microorganisms.

From this point of view, the present inventors have previously developed a photodegradable monofilament made of modified polyethylene into which a carbonyl group, which is a photosensitizing group, has been introduced into the main chain, and a photodegradable monofilament made of modified polyethylene and high-density polyethylene. I proposed about.

In particular, the latter photodegradable monofilament had high strength and had properties suitable as a fiber for industrial materials.

However, as a result of tracking the photodegradation behavior of this monofilament, we found that although it looks good, it disintegrates into small pieces or powder when exposed to light, but it does not decompose down to the level of 9 molecules, so if it is left on the ground. It has been found that there is a problem in that fragments or powdery substances formed by the disintegration remain in the soil and may have a negative impact on the soil.

The present inventors also proposed a microbially degradable monofilament made of high-density polyethylene blended with polycaprolactone. This monofilament naturally disintegrates in environments where microorganisms are actively active, such as in soil, sludge, and water, but after use, it is not necessarily placed in an environment where microorganisms are actively active. For example,
The problem was that if left on the ground, it would take an extremely long time to collapse.

(Problems to be Solved by the Invention) The present invention aims to provide a polyethylene monofilament that has high strength and is naturally disintegrated by light and microorganisms.

(Means for solving problems) The present invention solves the above problems.

The summary is as follows.

Main component is ethylene, 1.5-7.0% by weight
It consists of 20-50% by weight of modified polyethylene obtained by copolymerizing carbon monoxide or other ethylenically unsaturated compounds, 3-30% by weight of polycaprolactone, and 20-77% by weight of high-density polyethylene, and contains the following (a) A naturally disintegrating monofilament characterized by simultaneously satisfying the characteristics of ) to (c).

(a) Tensile strength 3g/d or more) Knot strength
2 g/d or more (c) Cutting elongation 5% or more 1 The present invention will be explained in detail.

The modified polyethylene used in the present invention is:

A photodegradable product containing ethylene as a main component and copolymerized with -carbon oxide or -carbon oxide and other ethylenically unsaturated compounds, with a -carbon oxide ratio of 1.5 to 76.
0% by weight, preferably 2.0-4.0% by weight. - If the copolymerization ratio of carbon oxide is less than 1.5% by weight, the photodecomposition rate is extremely low.

If it exceeds 7.0% by weight, the strength of the monofilament decreases and the rate of photodegradation becomes too high, resulting in a decrease in strength in a short period of time, making it impractical.

The photodecomposition rate can be controlled by the copolymerization ratio of carbon monoxide, and the copolymerization ratio of carbon monoxide is appropriately selected depending on the intended use of the monofilament.

Ethylenically unsaturated compounds used in the present invention include vinyl acetate, vinyl butyrate, (meth)acrylic acid,
Methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, maleic acid, fumaric acid,
Acrylonitrile, acrylamide, vinyl methyl ether, vinyl phenyl ether, styrene, vinyl chloride, propylene.

Butene-1, Hexene-1, Octene-1, Decene-1
, 4-methylpentene-1 and the like.

Vinyl acetate and ethyl acrylate are particularly preferred in terms of spinnability and mechanical properties, heat resistance, gloss, etc. of the resulting monofilament.

When ethylenically unsaturated compounds such as vinyl acetate and ethyl acrylate are copolymerized with carbon monoxide.

Photodecomposition can be caused rapidly after a certain period of time. When copolymerizing an ethylenically unsaturated compound, the copolymerization ratio is preferably 1 to 20% by weight.

The modified polyethylene in the present invention can be produced by a method disclosed in a patent publication such as Hiroshi.

US Patent 2497323 2641590 3083184 3
2483593530109 3676401 368
9460 36944123780140 38351
23 3929727 39488323948850
3948873 3968082 39843
884024104 4024325 40243
26 40769114143096 41373
g2 4139522 414309643048
87 Japanese Patent Publication 1986-128690 1982-128691 1982-115026 Hei 1i53723 Japanese Patent Publication 1977-39705 Specifically, 2 For example, , pressure 500
dilauroyl peroxide, tert-butyl peroxide under conditions of ~3000 atm.

Tertiary butyl perisobutyrate, tertiary
A free radical generator such as butyl peracetate or α,α°-azobisisobutyronitrile dissolved in an inert organic solvent such as benzene, kerosene or mineral oil is injected into the reactor, and ethylene, carbon monoxide and A method of copolymerizing with other ethylenically unsaturated compounds as necessary; In the presence of a catalyst or metal catalyst (Ziegler type, Natsuta type, Phillips type, etc.), ethylene and carbon monoxide and other ethylenically unsaturated compounds are mixed by a slurry method, solution method, gas phase method, etc. It can be produced by copolymerization.

Further, polycaprolactone is obtained by ring-opening polymerization of ε-caprolactone and has a melting point of about 60° C., and has a molecular weight of 10,000 to 10,000, preferably 20,000 to 50,000.

Furthermore, the high-density polyethylene used in the present invention has a density of 0.94 when manufactured by a normal low pressure method.
g/cut or more and a melt flow rate of 20 or less, preferably 2 or less.

The monofilament of the present invention is made of modified polyethylene 20~
50% by weight, 3-30% by weight of polycaprolactone and 20-77% by weight of high-density polyethylene. When the proportion of modified polyethylene is less than 20% by weight, the rate of photodegradation is low.

On the other hand, if it exceeds 50% by weight, the strength of the monofilament will be poor. In addition, the proportion of polycaprolactone is 3
When it is less than 3% by weight, the microbial decomposition rate is low;
If it exceeds 0% by weight, the strength of the monofilament will be poor. Furthermore, if the proportion of high-density polyethylene is less than 20% by weight, the strength of the monofilament will be significantly inferior.

On the other hand, if it exceeds 77% by weight, the natural disintegration rate of the monofilament due to light and microorganisms becomes extremely slow.

It becomes insufficient as a naturally disintegrating monofilament.

The method of mixing the three components constituting the monofilament is not particularly limited. Usually, a method is adopted in which the three components are melt-mixed in an extruder to form chips and then melt-spun, but the three components may be fed to a spinning device and mixed and spun.

The monofilament of the present invention can be manufactured by the following method.

First, a mixture of modified polyethylene, polycaprolactone, and high-density polyethylene in a predetermined ratio (usually melt-mixed chips) is subjected to melt spinning.
It is desirable to carry out at a temperature of 00°C. Spinning temperature 230℃
If it is less than 300°C, melt extrusion is difficult, and if it exceeds 300°C, the polymer will decompose.

It becomes difficult to obtain a high strength monofilament. The melt-spun monofilament is water-cooled.

- After being wound up, or without being wound up, it is continuously stretched in hot air or a heating medium such as heated water, glycerin, ethylene glycol, or silicone oil. Stretching conditions such as stretching temperature and stretching ratio are appropriately selected depending on the required performance of the target monofilament, but usually 60 to 1
At a temperature of about 10℃.

It is appropriate to stretch the film 10 to 17 times. In addition, it is desirable to perform the stretching in multiple stages of two or more stages, and in one stage stretching,
It is difficult to draw the monofilament sufficiently, making it difficult to obtain a high-strength monofilament. The drawn monofilament is then subjected to a relaxation heat treatment in an atmosphere at a temperature of 50 to 110°C to obtain a monofilament having desired strength and elongation characteristics. The appropriate relaxation rate at this time is 1 to 5%.

The monofilament of the present invention obtained in this way is
It has excellent strength and elongation properties and natural disintegration properties as described above.

In addition, those that do not have the above-mentioned strong elongation characteristics.

It is unsuitable as a monofilament for industrial materials.

Further, the fineness of the monofilament of the present invention is appropriately selected depending on the use, but is usually 50 d or more.

Note that the monofilament of the present invention may include, if necessary,
Polymers such as high-pressure low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ionomer, straight-line low-density ethylene-α-olefin copolymer, oxidation promoters, pigments, lubricants, Antistatic agent 1
Additives such as sunscreen inhibitors can be included.

(Function) The monofilament of the present invention is composed of photodegradable modified polyethylene, microbially degradable polycaprolactone, and ordinary high-density polyethylene.

Since light decomposes the modified polyethylene and microorganisms decompose polycaprolactone, the presence of light and/or microorganisms causes the monofilament to disintegrate.

In the present invention, the modified polyethylene is photodegradable, and the polycaprolactone is biodegradable.

High-density polyethylene contributes to its strength properties.

A monofilament with high strength and self-disintegrating properties can be obtained.

(Example) The present invention will be explained in more detail below with reference to Examples.

Note that the measurement method or evaluation method in the present invention is as follows.

Strength and elongation properties Measured according to JIS L 1013.

Natural disintegration The following photo-disintegration test and microbial disintegration test were conducted independently, and cases where both were good were evaluated as good.

■Photodegradation test Sunshine Weatherometer manufactured by Suga Test Instruments Co., Ltd. (Liver L-
Using 5UN-HC-)1), light was irradiated at 63°C for 40 hours.

The tensile strength after irradiation was measured, and the strength retention rate with respect to the initial strength was determined, and a case where the 1 strength retention rate was 60 to 90% was evaluated as having good photodegradability.

■ Microbial decay test If the sample is buried in soil at 10-25℃ for 6 months and then taken out, the monofilament shape has been lost, or the monofilament shape has been maintained but the tensile strength is 50% of the original value. The microbial disintegration property was evaluated to be good when the microbial disintegration property decreased to below.

Examples 1 to 17 and Comparative Examples 1 to 6 Modified polyethylene AI produced by copolymerizing 1.5 to 7.0% by weight of carbon monoxide produced by a high pressure method, with an average molecular weight of about 4
10,000 polycaprolactone B and melt flowray)
(measured according to JIS K 6760) is approximately 1.1g/
10 minutes of high-density polyethylene C set shown in Table 1! (
The mixture was supplied to a three-screw extruder for kneading so that the weight ratio of the mixture was obtained (weight ratio), and the mixture was melted and mixed to form chips.

This chip is fed to an extruder type melt spinning machine,
After melt-spinning at a spinning temperature of 290°C and cooling in a 10°C water bath, it is immediately introduced into a decalin bath at 80°C and subjected to first-stage stretching at a draw ratio of 8 to 12 times, followed by spinning in a glycerin bath at 95°C. 2nd stage stretching was performed at a stretching ratio of 1.3 to 1.7 times, and the relaxation rate was further increased to 3 to 6% in a heated atmosphere at 95°C.
A monofilament with a diameter of 0.2 to 0.3 μm was obtained.

Table 1 shows the characteristic values of the obtained monofilament.

Examples 18-25 7.0% by weight of carbon monoxide and vinyl acetate (Examples 18-21
) or 20% by weight of ethyl acrylate (Examples 22 to 25) and a modified polyethylene 82 copolymerized with the same test as in the above example.

The results are shown in Table 2.

Table 2 Note: C○ indicates the carbon monoxide copolymerization ratio of modified polyethylene A1.

(Effects of the Invention) According to the present invention, a polyethylene monofilament is provided which has strength and elongation properties almost comparable to those of ordinary polyethylene monofilament and has appropriate natural disintegration properties.

And one monofilament of the present invention is a fishing net.

Fishing line 6 Suitable as agricultural materials, etc., because if left in an environment where light and/or microorganisms exist after use, it will naturally disintegrate after a certain period of time.

By using the monofilament of the present invention, pollution can be prevented without requiring special waste treatment.

Claims (2)

[Claims] (1) Ethylene is the main component, 1.5 to 7.0
20 to 50% by weight of modified polyethylene copolymerized with carbon monoxide or other ethylenically unsaturated compounds
, 3 to 30% by weight of polycaprolactone and 20 to 77% by weight of high-density polyethylene, and the following (a) to (c)
) A naturally disintegrating monofilament characterized by simultaneously satisfying the following characteristics. (a) Tensile strength of 3 g/d or more (b) Knot strength of 2 g/d or more (c) Cutting elongation of 5% or more (2) The self-disintegrating monofilament according to claim 1, wherein the ethylenically unsaturated compound is vinyl acetate or ethyl acrylate.