JPS6212241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [] BACKGROUND TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin based on an aliphatic mono- or diolefin polymer in which an ultraviolet absorber is stably dispersed. In this invention, the "aliphatic mono- to diolefin polymer" is, for example, polyolefin (including polyethylene).

Since polyolefin was introduced to the world as a general-purpose plastic, it has been used for food packaging, general packaging, and other products, taking advantage of its superior strength, durability, moisture resistance, price, and film transparency.
It has come to be used in place of paper, wood, cellophane, metal, etc. in civil engineering, agriculture, and other fields.
It has become an essential material in modern society.

As the applications of polyolefins expand in this way, there is also an increasing demand for new functions not found in conventional polyolefins, such as particularly long-term or particularly high weather resistance and ultraviolet blocking properties to protect contents from ultraviolet rays. It's coming.

In order to impart weather resistance or ultraviolet blocking properties to resin materials, ultraviolet absorbers are generally added. However, in general, ultraviolet absorbers have poor compatibility with polyolefins, and even if they are added, they ooze out onto the surface of the polyolefin molded product, significantly impairing the appearance of the molded product, so the addition must be limited to a small amount. As a result, the weather resistance is not sufficiently improved, and the ultraviolet blocking property is also insufficient.

Some resins other than polyolefins do not have this problem. For example, methacrylic resins have particularly good compatibility with ultraviolet absorbers, allowing a large amount of ultraviolet absorbers to be added, resulting in resin materials with good ultraviolet blocking properties and good appearance.
However, methacrylic resin is too rigid and cannot be made into a flexible yet strong material like polyolefin. There are other resins that have good compatibility with UV absorbers, such as vinyl chloride resin and fluororesin, but they have to be used as general-purpose resin materials due to hygiene issues, mechanical properties such as strength and flexibility, and film molding methods. Due to problems such as price, it is only used in some fields.

[] Summary of the Invention The present invention aims to solve the above-mentioned problems and provide a polyolefin-based resin material with excellent ultraviolet blocking properties, by introducing an ultraviolet absorber in a specific embodiment. It aims to achieve this purpose.

Therefore, the method for producing a resin material with improved ultraviolet blocking properties according to the present invention requires (1) 50 to 99% by weight of aliphatic mono- or diolefin polymer particles and (2) vinyl or vinylidene monomer as an ultraviolet absorber. (3) a polymerization initiator; and (3) a polymerization initiator. It is characterized by impregnating the monomer into the polymer particles and then polymerizing the monomer.

Effects In the present invention, the ultraviolet absorber is added to the polyolefin particles by impregnating the ultraviolet absorber with a solution of a vinyl (including vinylidene) monomer and polymerizing the vinyl monomer in the polyolefin particles. It is immobilized in particles (which are of course not polyolefins themselves, but have been modified by polymers from vinyl monomers). A polyolefin-based thermoplastic resin into which an ultraviolet absorber is introduced by such a specific and limited method contains a necessary and sufficient amount of ultraviolet absorber, and there is no problem of leaching.

This effect of the present invention should be said to be unexpected. This is because, in addition to the method of the present invention, as a method for combining a polyolefin with a vinyl monomer or a vinyl polymer made from the same and an ultraviolet absorber, the ultraviolet absorber is kneaded into the polyolefin and then the vinyl monomer There are two methods: impregnating/polymerizing a polyolefin with a vinyl monomer and kneading a UV absorber into the polyolefin after impregnating/polymerizing a vinyl monomer, but the polyolefin-based resin materials obtained by these methods are both UV resistant. This is because the problems of absorbent seepage and escape are not solved. Furthermore, when a vinyl polymer mixed with an ultraviolet absorber is blended with a polyolefin, as is well known, the mechanical strength is significantly reduced due to interphase peeling phenomenon due to poor compatibility between the polyolefin and the vinyl polymer. It is ugly and has little practicality.

The method for producing the polyolefin-based resin material adopted in the present invention utilizes the techniques described in Japanese Patent Application Laid-Open Nos. 52-32990 and 52-50389. Therefore, these prior art techniques shall be utilized in the present invention as long as they do not contradict the spirit of the present invention.

[] Detailed description of the invention 1 Resin such as polyolefin This component accounts for at least 50% by weight of the resin material according to the present invention, and is generally an aliphatic mono- to diolefin polymer (sometimes referred to as resin such as polyolefin). One group of such polymers is homopolymers of aliphatic mono- or diolefins, and another group is copolymers of these olefins with each other or with copolymerizable monomers (of the latter copolymers). (in some cases, the content of these olefins is 50% by weight or more). "Copolymer" is intended to include random, block, and graft copolymers. Further, such polymers may be a mixture of each other or with a compatible polymer in an amount of up to 40% by weight of such polymer.

Examples of such polymers classified by monomer type include homopolymers of α-olefins (including ethylene) having about 2 to 20 carbon atoms, and copolymers of these with each other. , and copolymers with monomers copolymerizable with these (preferably those with an α-olefin content of 60% by weight or more). Specifically, for example, high pressure method, medium pressure method or low pressure method polyethylene, polypropylene, polybutene.
1, poly-4-methylpentene-1, ethylene-
Propylene random copolymer, ethylene-propylene block copolymer, propylene-butene-1
Random copolymer, propylene-ethylene-butene-1 random copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polypropylene,
etc. are representative examples. From the viewpoint of obtaining a general-purpose resin material, polyethylene, polypropylene, ethylene-propylene block or random copolymer, etc. are preferred.

In addition to such resinous polymers, the polymers of interest in the present invention may also have some degree of elasticity. Specifically, uncrosslinked or low crosslinked elastomers known as thermoplastic elastomers, such as ethylene-propylene (-diene) copolymer rubber, natural rubber, polyisobutylene rubber, butyl rubber, chlorobutyl rubber, polybutadiene, There are styrene-butadiene copolymers, etc. Also, a mixture of any amount of these and an olefin polymer may be used.

The resin used in the present invention is in the form of particles. The particle size is preferably 1 to 5 mm. Particle sizes smaller than the above can be used if the particle properties can be sufficiently maintained in an aqueous medium after impregnation with the vinyl monomer, while larger particles can also be used if a crushing operation is not required after polymerization. .

(2) Vinyl monomer As mentioned above, it contains vinylidene monomer.

Any radically polymerizable vinyl or vinylidene monomer can be used as long as it is capable of impregnating a given polyolefin or other resin particle in the aqueous medium in the required amount and at least partially dissolving the UV absorber.

Specific examples of vinyl or vinylidene monomers that can be used in the present invention include styrene and styrene derivatives, such as α-methylstyrene, vinyltoluene, chlorostyrene, methacrylic acid esters such as methyl methacrylate (especially C ₁ - C ₈ alkyl esters), acrylic esters (especially C ₁ -C ₈ alkyl esters) such as ethyl acrylate, conjugated dienes such as 1,3-butadiene, isoprene, vinyl such as vinyl acetate, etc. Examples include esters, unsaturated nitriles such as acrylonitrile and methacrylonitrile, and unsaturated mono- to dihalides such as vinyl chloride and vinylidene chloride. These can be used together. Further, a very small amount of a crosslinkable diene or polyene monomer, such as divinylbenzene, can be used in combination with such monomers.

The amount of the vinyl or vinylidene monomer is such that the polyolefin or other resin accounts for 50 to 99% and the vinyl or vinylidene monomer accounts for 50 to 1% by weight based on the total weight of the polyolefin or other resin.
Simply put, it is preferably about 1 to 100 parts by weight, particularly about 3 to 50 parts by weight, per 100 parts by weight of a resin such as polyolefin. If it is less than 1 part by weight (or less than 1% by weight based on the above-mentioned total amount), it is practically difficult to control the polymerization reaction and control the product. On the other hand, more than 100 parts by weight (same in terms of weight%)
If it exceeds 50%), not only can no further improvement in moldability be expected, but also the contribution of the mechanical strength of the resin such as polyolefin to the resulting resin material decreases. Furthermore, during impregnation or polymerization, a resin such as polyolefin is dissolved in these vinyl or vinylidene monomers, and the resulting modified particles may have irregular particle sizes or become blocked, making stirring impossible.

3. Ultraviolet Absorber Various ultraviolet absorbers that are known to be effective for the polyolefin and the like and for the polymer made from the vinyl monomer can be used.
However, since they are utilized as solutions in vinyl monomer, they should be soluble in vinyl monomer in significant concentrations. Note that if a given vinyl monomer cannot dissolve the required amount of ultraviolet absorber, an appropriate solvent can be used in combination.

Specific examples of the ultraviolet absorber used in the present invention are as follows. These may be used in combination within each group or between each group.

(1) Benzophenone series 2-hydroxy-4-n-octylbenzophenone 2-hydroxy-4-methoxy-2'-carboxybenzophenone 2-hydroxy-4-methoxybenzophenone, and others.

(2) Benzotriazole 2-(2'-hydroxy-3'-tert-butyl-
5′-methyl-phenyl)-5-chlorobenzotriazole (TINUVIN326) 2-(2′-hydroxy-3′,5′-di-tert-
Butyl-phenyl)-5-chlorobenzotriazole (TINUVIN327) 2-(2'-hydroxy-4'-octyl-phenyl)benzotriazole, and others.

(3) Salicylic acid series 4-t-butylphenyl salicylate, p-octylphenyl salicylate, and others.

(4) Benzoate-based 2,4-di-t-butylphenyl-3,5-
Di-t-butyl-4-hydroxybenzoate, others.

(5) Nickel phenolate type nickel-bis-octyl phenyl sulfite, and others.

These ultraviolet absorbers (UV) are utilized as solutions in vinyl monomer (VM). In that case, the concentration (UV/UV+VM×100) is 1 to 30% by weight.

4 Radical polymerization initiator In the present invention, resin particles such as polyolefin are impregnated with vinyl or vinylidene monomer in an aqueous medium without substantially polymerizing the monomer, and then this aqueous dispersion is heated to inject the monomer. The polymerization is usually promoted by a radical polymerization initiator. Moreover, this polymerization initiator must be able to be impregnated into resin particles such as polyolefin together with the monomer.

Therefore, the radical polymerization initiator used in the present invention is oil-soluble. Preferably, the decomposition temperature is 50 to 150°C to obtain a half-life of 10 hours. Here, "decomposition temperature to obtain a half-life of 10 hours" means that when 0.1 mol of a polymerization initiator is added to 1 liter of benzene and left at a certain temperature for 10 hours, the decomposition rate of the polymerization initiator is It means that temperature which is 50%. It goes without saying that if the impregnation step is carried out at a sufficiently low temperature, a polymerization initiator that is more decomposable at lower temperatures can be used.

A specific example of the radical polymerization initiator that can be used in the present invention is lauroyl peroxide (62
organic peroxides such as benzoyl peroxide (74°C), t-butyl peroxybenzoate (104°C), dicumyl peroxide (117°C), etc.
There are azo compounds such as azobisisobutyronitrile (65°C), and others (the temperature inside the cup is the half-life temperature mentioned above).

There is no limit to the amount of polymerization initiator, but it is generally about 0.01 to 10% by weight of the monomer weight used, usually 0.1 to 10% by weight.
It is about 2.0% by weight.

The polymerization initiator is usually used dissolved in vinyl or vinylidene monomer.

5 Impregnation of monomer into polyolefin resin particles in an aqueous medium A typical method for impregnating polyolefin resin particles with a vinyl or vinylidene monomer in an aqueous medium is to impregnate an aqueous dispersion of polyolefin resin particles. The process consists of adding a monomer in which a polymerization initiator (and other additives as necessary) is dissolved and stirring. Another method is to add resin particles such as polyolefin to an aqueous dispersion of a monomer dissolved in a polymerization initiator and stir the mixture.

During the impregnation process, virtually no polymerization occurs.
It should be operated at a sufficiently low temperature in relation to the decomposition temperature of the polymerization initiator used, generally between room temperature and 100°C.

In this step, the monomer is impregnated such that the amount of free monomer is 50% by weight or less of the amount of monomer used. Resins such as polyolefins are relatively compatible with vinyl or vinylidene monomers, so even if 50% by weight or more of the monomer is liberated before the start of polymerization, these monomers will be absorbed into the particles of resins such as polyolefins during polymerization. Since the particles are impregnated (including adhering), the polymer particles obtained by polymerizing these monomers do not precipitate independently from the modified polyolefin or other resin particles.

The impregnation time is usually about 2 to 8 hours.

The content of resin particles such as polyolefin and vinyl or vinylidene monomer in the aqueous dispersion is 100% of water.
It is usually about 5 to 100 parts by weight.

Such aqueous dispersions can be maintained in a stable dispersed state simply by sufficient stirring, but dispersions can be prepared more easily and stably by using an appropriate suspension stabilizer. can. As the suspension stabilizer in this case, those that can be used as a suspension stabilizer during aqueous suspension polymerization of vinyl or vinylidene monomers can generally be used, and
Specifically, water-soluble polymer substances such as polyvinyl alcohol, methylulose, and hydroxycellulose, anionic surfactants such as alkylbenzene sulfonates, nonionic surfactants such as polyoxyethylene alkyl ether, or Water-insoluble inorganic salts such as magnesium oxide and calcium phosphate are used alone or in combination in an amount of about 0.01 to 10% by weight based on water.

When impregnating resin particles such as polyolefin with vinyl or vinylidene monomers (and polymerization initiators), auxiliary materials such as plasticizers, lubricants, antioxidants, foaming agents, mold release agents, and colorants are simultaneously impregnated. (These auxiliary materials may already be added to the resin such as polyolefin, or they may be added after polymerization).

6 Polymerization If the aqueous dispersion thus prepared is heated to a temperature above which the polymerization initiator used decomposes at an appropriate rate, the impregnated vinyl or vinylidene monomer will polymerize. Resin particles such as modified polyolefin are generated. Since radical polymerization is to be carried out, heating should be carried out in an atmosphere substantially free of oxygen, and it is preferable to appropriately stir the aqueous dispersion during polymerization.

The polymerization temperature is determined in relation to the decomposition temperature of the polymerization initiator used, but is generally about 50 to 150°C. The polymerization temperature need not be constant throughout the polymerization period. The polymerization time is usually about 2 to 10 hours. The polymerization pressure is usually about normal pressure to 10 kg/cm ² .

In addition, n-butyl mercaptan,
It is preferable to add a chain transfer agent such as n-dodecyl mercaptan or t-dodecyl mercaptan.

After polymerization, if the same post-treatment as for ordinary aqueous suspension polymerization of vinyl or vinylidene monomers (e.g. styrene) is carried out, the shape of the resin particles used, such as polyolefin, is maintained almost unchanged, and it can be used immediately as a molding material. Modified polyolefin resin particles are obtained that can be used as.

The modified polyolefin resin of the present invention is a polyolefin resin containing a polymer made of uniformly dispersed vinyl or vinylidene monomers, or a resin in which vinyl or vinylidene monomer is grafted onto a polyolefin resin backbone, or It is presumed to be a mixture, and the polymer particles unique to the vinyl monomer do not exist separately from the resin particles such as polyolefin.

7. Utilization The resin such as modified polyolefin obtained in this way can be used as a resin material by itself.

The modified resins of the present invention may also be blended with compatible thermoplastic resins, such as polyolefin resins or polymers from vinyl or vinylidene monomers, the same or different from those used in the preparation of the modified resins. It can be used in the form of In particular, when used as a blend with a resin such as polyolefin, for example, when used as a blend of 5 to 95% by weight of modified resin/95 to 5% by weight of resin such as polyolefin, the improved properties of the modified resin of the present invention A resin composition that skillfully utilizes UV stability can be obtained. Both resins can be easily blended using a common resin kneading device.

The resin material obtained by the present invention can be used for various molded products,
It can be used to produce film fibers and other products.

8 Examples Example 1 In an autoclave with a capacity of 200 liters, 100 kg of pure water and 2 ml of tricalcium phosphate as a suspending agent.
Kg, and 3 g of sodium dodecylbenzenesulfonate as a suspension aid were added to form an aqueous medium. Separately, 750 g of ultraviolet absorber (TINUVIN327 manufactured by Ciba Geigy) and 142 g of t-butyl peroxybenzoate as a polymerization initiator were dissolved in 14.25 kg of methyl methacrylate, and this was added to the above aqueous medium, stirred, and suspended. Made it muddy. In addition, low-density polyethylene (density 0.918,
MI45) After introducing 35 kg of pellets and purging the inside of the autoclave with nitrogen gas, the system temperature was raised to 90°C and held for 3 hours to transfer methyl methacrylate containing a polymerization initiator and ultraviolet absorber to polyethylene. Impregnated into pellets.

This aqueous suspension was heated to 105°C and held for 3 hours to effect polymerization, and then heated to 120°C and held for 2 hours to complete polymerization. After cooling,
The contents were taken out and washed with acid and water to obtain modified polyethylene particles (ultraviolet absorber content 1.5% by weight, polymethyl methacrylate content 28.5% by weight) 50
Got Kg.

From this sample, a film with a thickness of 100μ was made.
The film was produced by inflation molding using a conventional method, and left in a gear oven at 80°C.The retention rate of the ultraviolet absorber in the film was tracked over time by measuring the change in concentration using an ultraviolet absorption spectrum. Almost no loss was observed, and the ultraviolet absorber retention rate after 10,000 hours was 98% or more. The results are shown in the attached drawing (curve 1).

Example 2 In the same manner as in Example 1, ultraviolet absorber 7.5
Kg, methyl methacrylate 17.5Kg, polymerization initiator 175
The amount of modified polyethylene (polymethyl methacrylate content: 35% by weight, ultraviolet absorber content: 15% by weight) was obtained by changing the amount of polyethylene (polymethyl methacrylate content: 35% by weight, UV absorber content: 15% by weight).

The thickness of this sample was measured in the same manner as in Example 1.
A 100μ film was made, and the retention rate of the ultraviolet absorber in the film was tracked over time. The results are shown in the drawing (curve 1). Moreover, the retention rate after 10,000 hours was 97% or more.

Example 3 100 parts by weight of the modified polyethylene obtained in Example 2 and 900 parts by weight of polyethylene (density 0.925, MI 2.8) were melt-kneaded and mixed in the same manner as in Example 1 to a thickness of 100μ.
was made into a film, and the retention rate of the ultraviolet absorber in the film was tracked over time.

The results are shown in the drawing (curve 1).
Also, the retention rate after 10,000 hours was 97% as in Example 2.
That's all.

Comparative example 1 Low density polyethylene (Yukalon NH50,
98.5 parts by weight of MI2.8, density 0.925) and 1.5 parts by weight of an ultraviolet absorber (TINUVIN327 manufactured by Ciba Geigy) were blended and
Pellets were obtained by melt-kneading at 160°C. A film having a thickness of 100 μm was produced from this pellet in the same manner as in Example 1. When we measured the change in the retention rate of the ultraviolet absorber on this film over time, we found that
The entire amount was lost in 500 hours. The results are shown in the drawing (curve 2).

Comparative Example 2 Ethylene-vinyl acetate copolymer (Yukalon
Comparative Example 1
A film with a thickness of 100 μm was produced by blending in the same manner as above. The change over time in the retention rate of the ultraviolet absorber in this film is as shown in the drawing (curve 3). In other words, the entire amount was lost in 2000 hours.

Comparative Example 3 Polymerization was carried out in the same system as in Example 1 except for the ultraviolet absorber, using 15 kg of methyl methacrylate, 150 g of polymerization initiator, and 35 kg of low-density polyethylene pellets to obtain modified polyethylene particles (polymethyl methacrylate). 50 kg (content 30% by weight) was obtained. this sample
100 parts by weight and an ultraviolet absorber (“TINUVIN327”)
1.5 parts by weight were blended and melt-kneaded at 160°C in an extruder with a 40 m/m diameter vent to obtain pellets.
A film with a thickness of 100 μm was produced from this pellet. When the retention rate of the ultraviolet absorber in this film was measured over time, the loss reached saturation after 1000 hours, and approximately 30% of the blended ultraviolet absorber remained.

The results are shown in the drawing (curve 4).

Reference example 1 Using the same method as in Example 1, ultraviolet absorber content 20
Modified polyethylene particles having a polymethyl methacrylate content of 30% by weight were produced. A film with a thickness of 100 μm was produced from this sample, but since this film contained more than a suitable amount of UV absorber, its strength was extremely low, resulting in film breakage and poor dispersion of the UV absorber. Furthermore, when the amount of UV absorber lost from this film was measured in the same manner as in Example 1, the retention rate reached saturation at 64%. This means that the concentration of UV absorber in the solution of methyl methacrylate and UV absorber during impregnation is approximately
This corresponds to 30% by weight. In other words, it is presumed that a concentration higher than this is undesirable.

Reference Example 2 Modified polyethylene (polymethyl methacrylate content 0.99% by weight) was prepared in the same manner as in Example 1 by changing the amounts of 5 g of ultraviolet absorber, 495 g of methyl methacrylate, 4.95 g of polymerization initiator, and 49.5 kg of low-density polyethylene. , UV absorber content 0.01%) 50Kg was obtained. A sheet with a thickness of 1 mm was made from this sample, and a box (cube) with sides of 10 cm was also made. A similar box was also made from a 1mm thick polyethylene sheet.
A commercially available oil confectionery (potato chips) with a peroxide value of 1.7 meq/Kg was placed in each container, and the mixture was placed 50 cm directly below a pure natural white fluorescent lamp for general lighting in a constant temperature and humidity room at 23°C and 50% humidity. After one month, the contents were taken out and the peroxide value was measured. There was a clear difference between 4.9 meq/Kg for modified polyethylene and 30.5 meq/Kg for regular polyethylene, indicating the effect of modified polyethylene. Ta.

However, the method for measuring peroxide value is as per the Ministry of Health and Welfare notification.
The method for measuring the peroxide value of instant noodles described in No. 17 was followed.

[Brief explanation of the drawing]

The drawing is a graph showing changes in ultraviolet absorber retention over time. Curve 1...Examples 1, 2 and 3, Curve 2...
Comparative example 1, curve 3... Comparative example 2, curve 4... Comparative example 3.

Claims (1)

[Claims] 1 Aliphatic mono- or diolefin polymer particles 50
~99% by weight, 50-1% by weight of a solution of a UV absorber in vinyl or vinylidene monomer (the UV absorber content in this solution is 1-30% by weight), and a polymerization initiator. and impregnating at least a major portion of this solution into the polymer particles, and then polymerizing the monomers. Manufacturing method.