JPS6211703A - Production of modified polyolefin - Google Patents

Abstract

PURPOSE:To suppress the induction of side reaction, offensive smell and coloring and obtain a modified polyolefin useful as various molded articles, etc., by the presence of a phosphoric acid based antioxidant on graft polymerizing a modifying agent onto a polyolefin in the presence of a peroxide. CONSTITUTION:A modifying agent, e.g. maleic anhydride, is graft polymerized onto a polyolefin, e.g. linear low-density polyethylene, preferably in a molten state in the presence of a peroxide, e.g. tert-butyl hydroperoxide. In the process, an antioxidant containing a phosphoric acid based antioxidant, e.g. distearyl- pentaerythritol diphosphite, is present in an amount of normally 0.01-1pts.wt. based on 100pts.wt. polyolefin. Preferably, the above-mentioned antioxidant contains a phenolic antioxidant within 1:0.1-1:2 weight ratio range based on the phosphoric acid based antioxidant in addition to the phosphoric acid based antioxidant.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to a method for producing a modified polyolefin.

[Background of the Invention] As a thermoplastic resin, polyolefin has excellent properties such as thermal stability, chemical resistance, and weather resistance, and is widely used in blow molded products, injection molded products, films, fibers, etc. .

Among polyolefins, linear low-density polyethylene in particular has been proposed for various uses utilizing its excellent physical properties.

Although these polyolefins are highly versatile resins, their physical properties such as adhesiveness and printability are inferior to other resins because they do not have polar functional groups in their molecules, which limits their range of use. ing.

In order to compensate for the above-mentioned drawbacks of polyolefins, a method of modifying polyolefins using a polar substance such as maleic anhydride has been used.

Generally, a modified polyolefin is produced by a method of graft polymerizing a polyolefin with a modifier such as maleic anhydride by heating in the presence of a reaction initiator.

Among the reaction initiators used in graft polymerization, peroxides are advantageous and widely used because they have good reactivity and a high grafting efficiency of the modifier to be grafted. As the peroxide, benzoyl peroxide or t-butyl peroxybenzoate is generally used.

[Problems with the Prior Art] When modifying a polyolefin, it is desirable that only a reaction in which a modifier is graft-polymerized to a polyolefin proceed. However, when peroxide is used, it acts as a reaction initiator for graft polymerization, and at the same time, some of the peroxide acts as a factor that induces side reactions such as oxidation reaction, crosslinking reaction, or decomposition reaction of polyolefin. Become.

The induced side reactions increase the gelling content of the modified polyolefin, resulting in problems such as the formation of so-called fish eyes when the modified polyolefin is formed into a film, and the modified polyolefin is colored yellow. Furthermore, some of the polyolefin decomposes.

There is a problem in that during the reaction, a bad odor is generated which is thought to be caused by the decomposition products, and the bad odor remains even in the obtained modified polyolefin, reducing the commercial value of the product.

Various attempts have been made to solve this problem, such as changing the structure of peroxide, but no effective solution has been found.

[Object of the invention] The present invention aims to suppress the progress of side reactions and gel the modified product without impairing the reactivity of peroxide used as a reaction initiator when graft polymerizing a modifying agent to a polyolefin. It is an object of the present invention to provide a method for producing a modified polyolefin, which can suppress the production of polyolefins and reduce the odor and coloring of the modified product.

[Summary of the Invention] The present invention provides a method for producing a modified polyolefin by graft polymerizing a modifier to a polyolefin in the presence of a peroxide. A method for producing a modified polyolefin is characterized by carrying out the following steps.

[Effects of the Invention] According to the production method of the present invention, it is possible to suppress the induction of side reactions without impairing the reactivity of the peroxide used as a reaction initiator when graft polymerizing a modifier to a polyolefin. Therefore, less gelation is produced, and odor and coloration of the modified product can be reduced.

[Detailed Description of the Invention] The present invention is directed to the graft polymerization of a polyolefin with a modifier such as maleic anhydride using a commonly used peroxide. The purpose is to prevent the progress of (side reactions) by adding a specific antioxidant and to selectively allow graft polymerization to progress.

Essentially, antioxidants act to eliminate radicals generated within resin components, thereby preventing oxidation of the resin. Therefore, if an antioxidant is added to a reaction system containing peroxide and graft polymerization is carried out, the radicals generated by the decomposition of the peroxide and the radicals generated in the resin component by these radicals will be absorbed by the antioxidant. It is thought that the reaction efficiency of graft polymerization decreases due to the action of antioxidants, and as far as the present inventors know, no attempt has been made to perform graft polymerization by adding an antioxidant to a reaction system using peroxide. .

However, according to the study conducted by the present inventor, the use of a specific type of antioxidant when graft polymerizing a modified product onto a polyolefin can prevent an extreme decrease in the efficiency of the graft polymerization reaction (e.g., graft efficiency). On the contrary, it was found that the progress of side reactions such as oxidation reactions, decomposition reactions, and crosslinking reactions of polyolefins was suppressed.

In other words, when a modifier is graft-polymerized to a polyolefin using a peroxide in the presence of an antioxidant containing a phosphorous antioxidant, side reactions such as oxidation reactions, decomposition reactions, or crosslinking reactions of the polyolefin are prevented. The progress of the graft polymerization reaction can be effectively suppressed9 and the efficiency of the graft polymerization reaction is not substantially reduced.

Examples of polyolefins used in graft polymerization include homopolymers or copolymers of α-olefins such as ethylene, propylene, phthene-1, pentene-1, hexene-1 and 4-methyl-pentene-1. . In addition to the above-mentioned copolymers, copolymers having polar groups such as ethylene/vinyl acetate copolymers may also be used.

In particular, polyolefins include polyethylene, polypropylene, and ethylene with small amounts of α-olefins having 3 to 10 carbon atoms (e.g., 1-butene, 1-pentene, hexene-1).
It is preferred to use a linear low density polyolefin consisting of a copolymer with 1).

As the modifier, one that is normally used as a modifier for polyolefins is used within the range of the usual usage amount. Examples of modifiers include maleic acid, itaconic acid and their anhydrides.

The reaction of graft polymerizing the above-mentioned modified product onto a polyolefin is started, for example, by adding a peroxide to a reaction system in which a polyolefin and a modifier are mixed, and heating the system to a temperature at which the peroxide decomposes. .

Examples of peroxides used as reaction initiators include t-butyl hydroperoxide, dialkyl peroxides [e.g., dicumyl peroxide, 2゜5-dimethyl-2,5-
di(t-butyl-peroxy)hexane, 1,3-bis-(t-butylperoxy-isopropyl)benzene], and peroxyesters [eg, t-butylhydroperoxy-benzene]. Peroxides are used within the normal usage range.

Various antioxidants are known, including phosphorus-based antioxidants, as antioxidants used to prevent the oxidation of polyolefins, etc., but the antioxidant used in the present invention contains at least a phosphorus-based antioxidant. .

As the phosphorus-based antioxidant, commonly used ones such as phosphite-based antioxidants and phenol/phosphite-based antioxidants can be used. Specific examples of phosphorus-based antioxidants include alkyl-pentaerythritol-diphosphite [e.g., distearyl-pentaerythritol-diphosphite], alkylphenyl-pentaerythritol-diphosphite, tris(
alkylphenyl) phosphites [e.g., tris(nonylphenyl)phosphite], dialkyl-aryl phosphites, diaryl-alkyl phosphites, and tetrakis(dialkylphenyl)-biphenylene diphosphonates [e.g., tetrakis(2,4-t- butylphenyl)-biphenylene diphosphonate, which can be used alone or in combination.

In particular, it is preferable to use distearyl-pentaerythritol-diphosphite, tris(nonylphenyl)phosphite, and tetrakis(di-t-butylphenyl)-biphenylene diphosphonate as the phosphorus antioxidant, either alone or in combination.

By using a combination of the above-mentioned phosphorus-based antioxidant and a non-phosphorus-based antioxidant, the effect of suppressing the progress of side reactions such as the oxidation reaction of polyolefins is further improved.

As antioxidants other than phosphorus antioxidants, it is possible to use commonly used antioxidants such as phenolic antioxidants and amine antioxidants, but especially Preference is given to using phenolic antioxidants.

When a phosphorus-based antioxidant and a phenolic antioxidant are used in combination, the phosphorus-based antioxidant mainly acts to reduce the odor and coloration of the modified polyolefin,
It is presumed that the phenolic antioxidant mainly suppresses the formation of gelatinized components, and that the two act synergistically to reduce odor and coloring and to suppress the formation of gelatinized components.

Examples of phenolic antioxidants include 2,6-di(
t-butyl-p-cresol), monoester-type high molecular weight hindered phenolic compounds [e.g., octadecyl-
3-(3,5-di-butyl-4-hydroxyphenyl)propionate], polycyclic hindered phenol compound [4°4°-isopropylidene-bis(2-t-butyl-phenol)], polymer type Polycyclic hindered phenol compounds and resorcinol compounds [e.g. 2,
4.6-)ribenzoyl-resorcinol, 2.4-dibenzoyl-resorcinol].

The antioxidant including the phosphorus antioxidant is usually used in an amount of 0.01 to 1 part by weight (preferably 0.03 to 0.2 part by weight) per 100 parts by weight of the polyolefin. In addition, when using a phosphorus antioxidant and a phenolic antioxidant in combination, the combined amount of both should normally be within the above range.

When a phosphorus antioxidant and a phenolic antioxidant are used in combination as antioxidants, the two are usually used in a blending weight ratio within the range of 1:0.1 to 1:2. In particular, it is preferable to use the ratio within the range of 1:0.5 to 1:1.5.

If the amount of antioxidant used is less than 0.1 part by weight, it may not be possible to effectively suppress the progress of side reactions. Furthermore, if the amount is more than 1 part by weight, the grafting efficiency of the modifier may decrease.

In addition, when using antioxidants other than phenolic antioxidants as antioxidants other than phosphoric acid antioxidants, they are usually used in the same ratio.

The antioxidant can be added by adding it alone, by mixing it with other additives, or by mixing a small amount of polyolefin with the antioxidant and other additives in advance. A variety of methods can be used, including methods of preparing a composition for use and adding this composition.

Examples of additives that may be mixed together when preparing the above additive composition include chlorine fixing agents (e.g., magnesium/aluminum-based chlorine fixing agents, calcium/strontium-based chlorine fixing agents), slip agents (e.g., metal soaps, composite metal soaps), and anti-blocking agents (eg, inorganic oxides such as silica).

Graft polymerization generally includes a method using a solvent and a method in which the polyolefin is heated to a molten state without using a solvent. can be used. However, when used in a method in which polyolefin is molten and graft polymerized, the antioxidant acts effectively on the highly reactive polyolefin in the molten state, resulting in less gelling and less odor and coloring. Fewer modified products can be produced.

The reaction conditions for graft polymerization when carrying out the present invention with the polyolefin in a molten state can be set to the same conditions as normal reaction conditions. For example, when using linear low-density polyolefin, the linear low-density polyolefin is heated to 110 to 280°C, and the reaction time is 0.
．． Set between 1 and 100 minutes. Further, the reaction is carried out using a conventional melt-kneading apparatus. An example of a melt-kneading device is an axle extruder. Note that the melt-kneading is preferably carried out in an atmosphere inert to polyolefins, such as a nitrogen atmosphere.

Furthermore, when the present invention is carried out using an extruder, it also has the effect of preventing oxidation of the surface of the screw of the extruder.

On the other hand, a method using a solvent involves, for example, dissolving or suspending the polyolefin and the modified product in an aromatic solvent, adding peroxide and an antioxidant containing a phosphorous antioxidant, and then After the graft polymerization is completed by heating under conventional conditions, a poor solvent such as a ketone or alcohol is added to precipitate the modified product. The modified polyolefin produced by this method is
When a modified product is precipitated and separated from a solvent, side reaction products that cause odor or coloring tend to remain in the solvent, so generally there is relatively little odor and coloring, but the method of the present invention By utilizing the production method, it is possible to produce a modified polyolefin with even less odor and coloring, and it is also possible to further reduce fish eyes when formed into a film.

The modified polyolefin obtained by the production method of the present invention has a low content of products resulting from side reactions such as oxidation reactions, and therefore has low odor and coloration.

Furthermore, since the gel content is low, for example, when formed into a film, there is less occurrence of fish eyes (100 pm or more), especially when a phosphorus antioxidant and a phenolic antioxidant are used in combination. To further reduce the formation of fish eyes (for example, 10 fish eyes/a
m” or less) is possible.

In addition, melt index (MI) due to graft polymerization
The range of fluctuation is also small.

Although it is possible to produce modified polyolefins with such properties, the grafting efficiency of the modified products [
(Graft polymerized modifier/modifier used)X100
] is equivalent to the case produced by the conventional method. For example, when maleic anhydride is used as the modified product, the grafting efficiency is usually 70 to 100 mol%.

Next, Examples and Comparative Examples of the present invention will be shown.

[Example 1] Melt index (MI) 2.0 g 710 minutes (measurement temperature 190°C), density 0.919 g/am", melting point 12
Linear low-density polyethylene (LL) with a molecular weight distribution (M w / M n ) of 3 and a butene-1 content of 4% by weight
DPE) is prepared, and 0.
After adding 0.96 x 10-' moles of tert-butyl hydroperoxide and 0.3 x 10-4 moles of maleic anhydride, this was combined with the additive composition 1.25 described below.
% by weight and mixed using a Henschel mixer, and the resulting mixture was extruded onto an axle Ja (screw diameter: 5
0+am, L/D = 24), heated to 220°C under a nitrogen atmosphere, and melt-kneaded for a residence time of -min to produce maleic acid-modified linear low-density polyethylene (modified product).

The additive composition contains LLDP, which is the same as the above-mentioned LLDPE.
4% by weight of dialkyl-pentaerythritol-diphosphite, 4% by weight of octadecyl-3-(3,5
-di-t-butyl-4-hydroxyphenyl) propionate and 4% by weight of calcium stearate were added and mixed.

The resulting modified product was 0.22X relative to LLDPElg.
IO-4 mol of maleic anhydride is graft polymerized (grafting efficiency 73.3 mol%), MIo, 75g71
0 min, density 0.919 g/cm', and melting point 123
It was ℃.

The obtained modified product was molded into a film, and the number of fish eyes with a diameter of 100 gm or more per cm was counted to be 8.

[Comparative Example 1] Maleic acid-modified linear low-density polyethylene was produced in the same manner as in Example 1, except that an additive composition not containing dialkyl-pentaerythritol-diphosphite was prepared and used.

The obtained modified product has a ratio of 0.2 to 1 g of LLDPE.
3X10-4 mol of maleic anhydride was grafted (grafting efficiency 76.7 mol%), MIo, 67 g
710 minutes, density 0.919 g/Cg, melting point 123°C.

The number of fish eyes counted in the same manner as in Example 1 was 30.

[Comparative Example 2] In Example 1, LLDPE was used instead of the additive composition.
Maleic acid modified in the same manner except that an additive composition prepared by adding and mixing 4% by weight of octadecyl-3-(3°5-di-t-butyl-4-hydroxyphenyl)propionate was used. Linear low density polyethylene was produced.

The obtained modified product was 0.2% per 1 g of LLDPE.
2×10-' mol of maleic anhydride was grafted (grafting efficiency 73.3 mol%), MIo, 73 g
710 minutes, density 0.919g/crtf, melting point 123°C
Met.

The number of fish eyes counted in the same manner as in Example 1 was 18.

The maleic acid-modified linear low-density polyethylene produced in Example 1 and Comparative Examples 1 and 2 was placed in a sealed container, heated together with the container at 80°C for one hour, and 10 testers evaluated the odor inside the container. We ranked the strength (
blind test).

As a result, the odor of the modified product produced in Example 1 was weaker than that of the two types of modified products produced in Comparative Example, and the odor of the modified product produced in Comparative Example 2 was weaker than that of the modified product produced in Comparative Example 1. All testers judged it to be slightly weaker than the odor.

Measurement of discoloration The yellowness of the obtained maleic acid-modified polyethylene was measured (measuring device, manufactured by Nippon Heavy Shiki ■, NDloolDP).

As a result, the yellowness of the modified product produced in Example 1 was lower than that of the modified products produced in Comparative Examples 1 and 2, and when the modified product produced in Comparative Example 1 and the modified product produced in Comparative Example 2 were compared, The yellowness of the product produced in Example 2 was high.

Claims (1)

[Claims] 1. A method for producing a modified polyolefin by graft polymerizing a modifier to a polyolefin in the presence of a peroxide, the graft polymerization being carried out in the presence of an antioxidant including a phosphorous antioxidant. 1. A method for producing a modified polyolefin, characterized by carrying out the following steps. 2. The method for producing a modified polyolefin according to claim 1, wherein the polyolefin is in a molten state when graft polymerizing the modifier. 3. Phosphorous antioxidants include distearyl-pentaerythritol-diphosphite and tris(nonylphenyl)
The modified polyolefin according to claim 1, which is at least one phosphorus antioxidant selected from the group consisting of phosphite and tetrakis(di-t-butylphenyl)-biphenylene diphosphonate. manufacturing method. 4. The method according to claim 1, wherein the amount of the antioxidant including the phosphorus antioxidant is within the range of 0.01 to 1 part by weight per 100 parts by weight of the polyolefin. A method for producing modified polyolefin. 5. The method for producing a modified polyolefin according to claim 1, wherein the antioxidant contains a phenolic antioxidant in addition to a phosphorous antioxidant. 6. Production of a modified polyolefin according to claim 5, wherein the weight ratio of the phosphorus antioxidant to the phenolic antioxidant is within the range of 1:0.1 to 1:2. Method. 7. The method for producing a modified polyolefin according to claim 1, wherein the modifier is maleic anhydride. 8. The method for producing a modified polyolefin according to claim 1, wherein the polyolefin is linear low-density polyethylene.