JP2000290313A - Grafting method of olefin polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing a polyolefin wherein an ethylenically unsaturated carboxylic acid of high quality is safely grafted without use of a hazadous organic solvent. SOLUTION: 100 pts.wt. of an olefin polymer component (a) wherein a 8 mesh-on component of high quality is present in an amount of 10 wt.% or below when a particle size thereof is measured according to ASTM (D-1291-63), 0.1 to 3.0 pts.wt. of an ethylenically unsaturated carboxylic acid or its derivative (b), and 0.01 to 0.5 pts.wt. of a free-radical initiator (c) are reacted by melting and kneading in a twin-screw extruder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the reactive extrusion of a mixture of a molten olefin polymer (sometimes referred to as a polyolefin), a graftable ethylenically unsaturated carboxylic acid or a derivative thereof, and a radical initiator. The present invention relates to a continuous method for grafting an olefin-based polymer, and more particularly to a continuous method for grafting a linear olefin polyolefin.

[0002]

2. Description of the Prior Art The technology of modifying the properties of polyolefins by grafting the polyolefins as a melt in an extruder is well known. The thus obtained grafted polyolefin is widely used for applications such as, for example, coating modification and adhesion to polar materials. In particular, polyolefins grafted with ethylenically unsaturated carboxylic acids and their derivatives show excellent modifying performance, and among them, maleic anhydride grafted polyolefins are widely used as adhesive resins with good performance, including food packaging materials. ing.

[0003] Methods for preparing polyolefins grafted with ethylenically unsaturated carboxylic acids and their derivatives are well documented by those skilled in the art. Typically, maleic anhydride and a molten olefin polymer are reacted under conditions of high shear stress. A wide range of mixing devices are generally described as suitable.

[0004] However, even if an attempt is made to produce a highly modified product with high productivity using a twin-screw extruder, unreacted products of ethylenically unsaturated carboxylic acid generally remain in the pellets, and this is a problem in foods. When a packaging material has an unpleasant odor or when a grafted polyolefin is formed into a film, a problem occurs in that gel is frequently generated on the film. These problems could be alleviated by minimizing the amount of ethylenically unsaturated carboxylic acid to be grafted and by providing a very powerful deaerator in the extruder, but could not be said to be sufficient.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-216032, a technique for delaying the introduction of an antioxidant into an extruder has been proposed. Here, attention is paid to the stability of the melt index. There is no gel generation suppressing effect. No. 2666080 discloses that maleic anhydride is dissolved in a solvent and injected into an extruder to improve odor, gel, and hue.However, this method has a risk of ignition in a high-temperature extruder. In order to inject a certain organic solvent, in actual production, the equipment itself needs to have a special explosion-proof structure,
It can also be said that there is a problem in safety.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polyolefin grafted with a safe and high-quality ethylenically unsaturated carboxylic acid without using a dangerous organic solvent. Specifically, the present invention provides a new and simple method that enables the gel level and the amount of residual ethylenically unsaturated carboxylic acid to be kept low even when the graft amount is increased.

Another object of the present invention is to provide a high-quality highly ethylenically unsaturated carboxylic acid-grafted polyolefin, and to obtain a grafted polyolefin having a low gelation even when diluted and used to form a film. To provide.

In the present invention, attention has been paid to the dispersion and reaction behavior of the polyolefin in the extruder, and studies have been continued. As a result, when polyolefin having a specific particle size is used as a raw material, the reaction is found to be performed efficiently,
The present invention has been reached.

[0009]

According to the present invention, the above objects and advantages of the present invention are as follows: (1) The amount of a component having a particle size of 8 mesh on as measured by ASTM (D-1291-63) is 10 100 parts by weight of the olefin polymer component (a) of 0.1% by weight or less, 0.1 to 3.0 parts by weight of the ethylenically unsaturated carboxylic acid or its derivative (b), and 0.01 of the radical initiator (c). A method for producing a grafted olefin polymer, comprising melting and kneading 0.5 to 0.5 parts by weight with a twin-screw extruder to cause a reaction. (2) The olefin polymer component (a) has the following (a-1)
To (a-4), which is an olefin polymer selected from (a-4), (a-1) high-density polyethylene, (a-2)
High-pressure low-density polyethylene, (a-3) a linear copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, (a-4)
This is achieved by a linear copolymer of ethylene and an unsaturated carboxylic acid or a derivative thereof.

<Olefin Polymer> As the olefin polymer (a) that can be used in the present invention, those mainly composed of ethylene and propylene are used.
1) a high-density polyethylene, (a-2) a high-pressure low-density polyethylene, (a-3) a linear copolymer of ethylene and 1 to 5 mol% of an α-olefin having 3 to 10 carbon atoms, a
-4) An olefin polymer selected from linear copolymers of ethylene and less than 10 mol% of an unsaturated carboxylic acid or a derivative thereof is preferred. Here, as the unsaturated carboxylic acid or derivative thereof in (a-4), acrylic acid,
It is preferably selected from the group consisting of methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and vinyl acetate.

The olefin polymer (a) that can be used in the present invention is usually a melt flow rate (ISO standard 1133-19).
Measured at 2.16 kg load and 190 ° C. according to 91) is at least 0.1 g / 10 min, preferably at least 0.5 g / 10 min.
In most cases, the melt flow rate will not exceed 50 g / 10 minutes, and more preferably will not exceed 40 g / 10 minutes.

<Method of adjusting particle size of olefin polymer> In the present invention, it is necessary that the olefin polymer (a) has a certain particle size. The method of adjusting the particle size of the olefin polymer (a) is generally a method of mechanical pulverization at room temperature or in a state of cooling with liquid nitrogen, but using a polyolefin powder immediately after polymerization obtained by gas phase polymerization or slurry polymerization. You can also.

The particle size of the olefin polymer (a) is AS
As a result of a measurement according to the method of TM (D-1291-63), the content of the 8 mesh-on component is 10% by weight or less, preferably 5% by weight or less. When the content of the 8 mesh-on component is 10% by weight or less, the reaction becomes uniform, and gel generation is suppressed.
In the present invention, the object can be achieved simply by using an olefin polymer passed through a sieve of 9 mesh or more.

<Extruder> A twin-screw extruder is suitable for the extruder used in the present invention. Generally, the screw of an extruder is composed of a combination of a segment for conveying a resin and a segment for kneading. The composition of the extruder and the shape of the screw are not particularly limited, but in order to carry out the reaction sufficiently, it is necessary to raise the temperature sufficiently and to have an appropriate residence time.
It is preferable to be designed to have more than one kneading portion. In addition, it is preferable that a vent for removing unreacted ethylenically unsaturated carboxylic acid is provided in an intermediate portion of the extruder.

<Radical initiator> The grafting reaction in the method of the present invention is initiated by the decomposition of the radical initiator to generate free radicals. Preferably, an organic peroxide is used as the radical initiator. As a kind of the organic peroxide, a decomposition temperature for obtaining a half life of 1 minute is 120 ° C. to 260 ° C., preferably 140 ° C. to 230 ° C.

If the decomposition temperature is too low, the decomposition reaction starts in a state where the organic peroxide is not sufficiently dispersed, so that gel is easily generated. If the decomposition temperature is too high, a sufficient reaction cannot be achieved within the residence time of the extruder. Therefore, unreacted ethylenically unsaturated carboxylic acid tends to remain in the resin.

Specific examples of organic peroxides include 1,1,
1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, ditertiary butyl peroxide, diisopropylbenzene hydroperoxide, tertiary butyl Cumyl peroxide, α, α '
-Bis (tert-butylperoxy-meta-isopropyl) benzene, 2,5-dimethyl-2,5-di (tertiarybutylperoxy) hexane, dicumyl peroxide, ditertiarybutyldiperoxyisophthalate, n -Butyl-4,4-bis (tert-butylperoxy) valerate, tert-butylperoxybenzoate, tert-butylperoxyacetate, cyclohexanone peroxide, tert-butylperoxylaurate, benzoyl peroxide, acetyl peroxide And the like. Above all, 2,5-
Dimethyl-2,5-di (tert-butylperoxy) hexyne-3, di-tert-butyl peroxide, diisopropylbenzene hydroperoxide, 2,5-
Dimethyl-2,5-di (tert-butylperoxy) hexane is preferably used.

<Ethylenically unsaturated carboxylic acid> Examples of the ethylenically unsaturated carboxylic acid or its derivative (b) in the method of the present invention include acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid and mesaconic acid. , Maleic anhydride, hymic anhydride, 4-methylcyclohex-4-en-1,2-dicarboxylic anhydride,
Bicyclo (2.2.2) oct-5-ene-2,3-dicarboxylic anhydride, 1,2,3,4,5,8,9,10
-Octahydronaphthalene-2,3-dicarboxylic anhydride, 2-oxa-1,3-diketospiro (4.4) non-7-ene, bicyclo (2.2.1) hept-5-ene-2, 3-dicarboxylic anhydride, maleopimaric acid, tetrahydrophthalic anhydride, x-methyl-bicyclo (2.
2.1) Hept-5-ene-2,3-dicarboxylic anhydride, x-methyl-norbornene-5-ene-2,3-dicarboxylic anhydride, norbornene-5-ene-2,3-
Dicarboxylic anhydrides may be mentioned. Acid anhydrides are preferably used, and among them, maleic anhydride and hymic anhydride are suitable.

<Antioxidant> In the method of the present invention, any of the known antioxidants for polyolefins is used as the antioxidant. Generally, a compound having a hindered phenol group and a phosphorus compound are used.

More specifically, 3,5-di-tert-butyl-4-hydroxytoluene, n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-tert-butylphenyl) propionate, tetrakis (methylene) -3 (3,5-ditert-butyl-4-hydroxyphenyl) propionate) methane, 1,3,5-trimethyl-
2,4,6-tris (3,5-di-tert-butyl-
4-hydroxyphenyl) benzylbenzene, tris (2,4-di-tert-butylphenyl) phosphite, tris (monononylphenyl) phosphite,
Tris (dinonylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) 4,4-
Biphenylenediphosphonite is exemplified.

<Method of Injecting Raw Materials> In the method of the present invention, it is necessary to thoroughly mix the radical initiator and the olefin polymer powder whose particle size has been adjusted before the extruder is introduced. At that time, the radical initiator may be diluted with a solvent in order to adjust the viscosity of the radical initiator. Alternatively, a part of the raw material whose particle size has been adjusted with the radical initiator may be impregnated in advance, and this may be uniformly mixed with the remaining raw materials.

The ethylenically unsaturated carboxylic acid and its derivative may be mixed with an olefin polymer in a pre-ground state and then introduced into an extruder, or the ethylenically unsaturated carboxylic acid and its derivative may be melted, It is preferable to introduce the resin at the entrance or midway of the extruder before the first kneading zone of the extruder at which the resin temperature reaches 200 ° C.

The amounts of the radical initiator, the ethylenically unsaturated carboxylic acid and the derivatives thereof vary depending on the desired graft ratio.
The amount of the ethylenically unsaturated carboxylic acid and its derivative is from 0.05 to 3 parts by weight, preferably from 0.1 to 2 parts by weight, based on part by weight. Especially 0.
When it is blended in an amount of 5 parts by weight or more and 3 parts by weight or less, a good film appearance characteristic of the present method is obtained.

The amount of the radical initiator is usually at least 0.01 part by weight and not more than 1 part by weight, preferably not less than 0.03 part by weight and not more than 0.5 part by weight, based on 100 parts by weight of the polyolefin.

The ratio of the ethylenically unsaturated carboxylic acid and its derivative to the radical initiator is usually 50/1 to 1 by weight.
5/1, preferably 30/1 to 8/1. If the amount of the radical initiator is too small, the grafting reaction does not proceed, and if the amount of the radical initiator is too large, the crosslinking reaction precedes and a large amount of gel is generated.

The content of the antioxidant is olefin polymer 1
It is preferably 0.02 to 2 parts by weight based on 00 parts by weight. The antioxidant is added to an extruder after at least one or more of the above-mentioned antioxidants are mixed with an olefin polymer in advance.

<Grafted Olefin Polymer> The grafted olefin polymer produced by the above method has a melt flow rate of 0.05 to 30 g / 10 minutes, and has a grafted ethylenically unsaturated carboxylic acid. The amount of acid and its derivative is 100% by weight of the olefin polymer.
0.1 to 3.0% by weight. Further, the amount of the grafted ethylenically unsaturated carboxylic acid and its derivative is preferably from 0.3% by weight to 2.0% by weight.

When produced by the same method, the amount of unreacted ethylenically unsaturated carboxylic acid and its derivative in the pellet is less than 0.5 part by weight based on 100 parts by weight of the olefin polymer.

[0029]

According to the present invention, a grafted olefin polymer having a high degree of modification can be produced safely and economically. In addition, the grafted olefin polymer produced according to the present invention has a low gel content due to the localization of the graft reaction and a small amount of residual monomer. It can also be used as a resin.

[0030]

Next, the present invention will be described with reference to examples. Examples 1-2 and Comparative Examples 1-3.

Example 1 <Extruder> ZSK 57 mm twin-screw extruder (L / D = 36, manufactured by W & P) Set temperature C1 C2 C3 C4 C5-Die Cooling 150 180 210 250 ° C. Screen mesh 80/20/80 mesh Screw rotation speed 250rpm Feed amount 50kg / hr

<Olefin Polymer> Raw material LLDPE (ethylene / butene-1 copolymer, density 0.923, melt flow rate = 2, 10 after mechanical pulverization)
Mesh pass product) 8 mesh on ingredient amount 0% by weight

<Radical initiator> 2,5-dimethyl-2,5-di (tert-butylperoxy) hexine-3 (manufactured by NOF CORPORATION, trade name: Perhexin 25B) 100 parts by weight of polyethylene resin 0.078 parts by weight were mixed and mixed with a Henschel mixer.

<Ethylene Unsaturated Carboxylic Acid and Derivative Thereof> Granule maleic anhydride (Crystalman, manufactured by NOF CORPORATION) was mixed with 0.8 part by weight with respect to 100 parts by weight of a polyethylene resin to obtain a Henschel mixer. And mixed.

<Antioxidant> Tetrakis (methylene-3)
(3,5-Ditert-butyl-4-hydroxyphenyl) propionate) methane (trade name Irganox 1)
010, manufactured by Ciba Geigy Co., Ltd.)
0.1 parts by weight was blended with respect to 0 parts by weight and mixed with a Henschel mixer.

<Mixing> The above LLDPE, 2,5-dimethyl
-2,5-di (tert-butylperoxy) hexyne-3
(Manufactured by NOF CORPORATION, trade name: Perhexin 25B), maleic anhydride, tetrakis (methylene-3 (3,5-ditert-butyl-4-hydroxyphenyl) propionate) methane (trade name: Irganox 1010, Ciba-Geigy) )) Was sufficiently mixed with a Henschel mixer and then introduced into an extruder.

<Grafted polyethylene> Melt flow rate of grafted polyethylene (190 ° C., 2.16 kg load)
Is 0.30 g / 10 minutes, and the grafting amount of maleic anhydride is 0.8% by weight based on 100% by weight of grafted LLDPE.
And the residual unreacted maleic acid is grafted LLDPE
0.003 parts by weight per 100 parts by weight.

20 parts by weight of the grafted polyethylene were blended with 80 parts by weight of LLDPE for film having a melt flow rate of 2 to form a 50 μm single-layer cast film at 220 ° C. When gels of 0.2 mm or more in the film were counted, the number was 42 / m ² .

Comparative Example 1 The procedure of Example 1 was repeated, except that the polyethylene before grinding was used. 100% by weight of 8-mesh-on component in polyethylene before grinding
Met.

The grafted polyethylene had a melt flow rate (190 ° C., 2.16 kg load) of 0.28 g / 10 min, and the amount of grafting was 0.8 with respect to 100% by weight of the grafted LLDPE.
% By weight, and the residual unreacted maleic acid is grafted LL
0.005 parts by weight based on 100 parts by weight of DPE.

20 parts by weight of the grafted polyethylene were used in the same manner as in Example 1 for melt flow rate = 2
Blend with 80 parts by weight of LDPE, 50μm at 220 ° C
Of a single-layer cast film.
When gels of 2 mm or more were counted, 81 gels / m ²
Met.

Example 2 As an olefin polymer, L
LDPE (ethylene / butene-1 copolymer, density 0.92
5, melt flow rate = 12, 10 mesh pass product after mechanical pulverization) The same operation as in Example 1 was carried out except that an 8 mesh-on component amount of 0% by weight was used.

The melt flow rate of the grafted polyethylene (190 ° C., 2.16 kg load) was 3.2 g / 10 minutes, the graft amount was 0.8% by weight based on 100% by weight of the grafted LLDPE, and the residual unreacted maleic acid was used. Is the grafted LLDP
It was 0.0028 parts by weight based on 100 parts by weight of E.

20 parts by weight of the grafted polyethylene were used in the same manner as in Example 1 for melt flow rate = 2
Blend with 80 parts by weight of LDPE, 50μm at 220 ° C
Of a single-layer cast film.
When gels of 2 mm or more were counted, the number was 29 / m ² .

Comparative Example 2 The same procedure as in Example 1 was carried out except that the polyethylene before grinding was used. 100% by weight of 8-mesh-on component in polyethylene before grinding
Met.

The melt flow rate of the grafted polyethylene (190 ° C., 2.16 kg load) was 3.0 g / 10 minutes, the amount of grafting was 0.8% by weight based on 100% by weight of the grafted LLDPE, and residual unreacted maleic acid was used. Is the grafted LLDP
0.0075 parts by weight based on 100 parts by weight of E.

20 parts by weight of the grafted polyethylene were used in the same manner as in Example 1 for melt flow rate = 2
Blend with 80 parts by weight of LDPE, 50μm at 220 ° C
Of a single-layer cast film.
When counting gels of 2 mm or more, 130 gels / m ²
Met.

Comparative Example 3 The procedure of Example 1 was repeated except that 75 parts by weight of the pulverized polyethylene used in Example 1 and 25 parts by weight of the unpulverized polyethylene used in Comparative Example 1 were previously blended with a tumbler. Performed similarly to 1.

The melt flow rate of the grafted polyethylene (190 ° C., 2.16 kg load) was 0.22 g / 10 minutes, and the graft amount was 0.8 with respect to 100% by weight of the grafted LLDPE.
% By weight, and the residual unreacted maleic acid is grafted LL
0.0007 parts by weight based on 100 parts by weight of DPE.

20 parts by weight of the grafted polyethylene were used in the same manner as in Example 1 for melt flow rate = 2
Blend with 80 parts by weight of LDPE, 50μm at 220 ° C
Of a single-layer cast film.
When gels of 2 mm or more were counted, 112 gels / m ²
Met.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) (C08F 255/00 222: 06)

Claims (2)

[Claims] 1. 100 parts by weight of an olefin-based polymer component (a) having a particle size of 8 mesh-on as measured by ASTM (D-1291-63) of 10% by weight or less, and ethylenically unsaturated 0.1 to 3.0 parts by weight of a carboxylic acid or a derivative thereof (b) and 0.01 of a radical initiator (c)
A method for producing a grafted olefin polymer, comprising melting and kneading 0.5 to 0.5 parts by weight with a twin-screw extruder to cause a reaction. 2. An olefin polymer component (a) comprising:
The method according to claim 1, which is an olefin polymer selected from (a-1) to (a-4), (a-1) high-density polyethylene, (a-2) high-pressure low-density polyethylene, (a-3) ) Ethylene and α- having 3 to 10 carbon atoms
Linear copolymers of olefins and (a-4) linear copolymers of ethylene and unsaturated carboxylic acids or derivatives thereof.