JPH06322218A - Acrylic plastisol composition excellent in creep resistance - Google Patents

Abstract

PURPOSE:To obtain an acrylic plastisol composition excellent in the retention of flow during long-term storage and gelation performances upon heating by dispersing an acrylic resin having a specified functional group in a plasticizer containing a cross-linking agent reactive with the functional group. CONSTITUTION:A plastisol consisting of a dispersion medium based on a plasticizer and acrylic resin particles dispersed in the medium, wherein the resin is an acrylic resin having a functional group selected from among a carboxyl group, a group of its salt, a hydroxyl group, an epoxy group, a methylol group and an ether methylol group, and the medium contains the cross-linking agent in a state at least partially solubilized in the medium, is provided. In this composition, the functional groups present in the acrylic resin prevent the acrylic resin from compatibilizing with the plasticizer during storage at room temperature to prolong the pot life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastisol composition which gives a coating or a molded product having excellent creep resistance, and more specifically, it is excellent in coating and molding required for long-term storage. The present invention relates to a plastisol composition in which the fluidity is maintained, while exhibiting excellent gelling performance upon heating, and the formed coating or molded article is an acrylic resin-based plastisol.

[0002]

2. Description of the Related Art Gaskets, liners, etc. used for sealing container lids, etc. have excellent fluidity, do not contain volatilizing components such as solvents, etc. The plastisol composition is widely used because it has appropriate flexibility and cushioning properties.

This plastisol uses a liquid plasticizer as a dispersion medium and has emulsion-sized or suspension-sized resin particles dispersed therein, and the dispersed state is maintained at room temperature, but the resin particles are dispersed at high temperature. By absorbing the plasticizer, the resin particles are coalesced and plasticized. As the resin, vinyl chloride homopolymers and copolymers have been widely used, but when incinerated, they prevent the release of hydrogen chloride into the atmosphere, and further produce harmful substances such as dioxins. The use of plastisols has already been proposed.

For example, Japanese Examined Patent Publication No. 56-26263 includes particles of a single phase surfactant-free acrylic polymer or copolymer containing at least 60% by weight of alkyl acrylate or methacrylate units. And thus includes a compatible liquid plasticizer whose polymer or copolymer is non-volatile at room temperature and is not a monomer having the same chemical structure as the monomer of said polymer or copolymer. A heat-coalescent acrylic resin plastisol characterized by being dispersed in a surfactant-free medium is described.

Further, non-vinyl chloride resin type reactive plastisols are already known, for example, Japanese Patent Publication No. 1-127.
No. 72 discloses a reactive plastisol composed of a polyvinyl acetal resin which is insoluble in a plasticizer at room temperature and is plastic at a high temperature, an epoxy resin or a combination thereof with a polyester plasticizer, and a curing agent for the epoxy resin. ing.

Further, JP-A-62-161849 discloses a reactive plastisol comprising a polymethacrylate resin, a polyether or polyester type plasticizer modified with isocyanate or the like, and a thermal reaction initiator or a photoreaction initiator. Has been done.

[0007]

However, the known acrylic plastisols seen in the former proposal have a drawback that they have a poor pot life as compared with vinyl chloride resin-based plastisol compositions. It has the disadvantages of low fluidity and insufficient gelling performance after storage, and the creep resistance of the coating or molded article after gelation by heating, especially the resistance to heating. It has a drawback that creep property is not sufficient.

For example, a container or a container lid is provided with a gasket or a lining formed of a plastisol lining for the purpose of sealing, but one formed of an acrylic resin plastisol is formed of a vinyl chloride resin plastisol. Compared to the above, the creep resistance is significantly inferior, and due to the heat during hot filling and retort sterilization,
Trouble such as creep and breakage occurs, causing a problem of leakage.

Therefore, the object of the present invention is to maintain the excellent fluidity required for coating, molding, etc. even during long-term storage, to exhibit an excellent gelling property upon heating, and to obtain the obtained coating or molded article. Is to provide an acrylic resin-based plastisol composition exhibiting significantly improved creep resistance.

[0010]

According to the present invention, in a plastisol composition comprising a dispersion medium mainly containing a plasticizer and acrylic resin particles dispersed in the dispersion medium, the acrylic resin particles are Carboxyl group, its salt group,
Acrylic resin particles having a functional group selected from the group consisting of a hydroxyl group, an epoxy group, a methylol group and an etherified methylol group, wherein the dispersion medium is a cross-linking agent having reactivity with the functional group. Provided is an acrylic plastisol composition having excellent creep resistance, which is contained in a state of being at least partially solubilized therein.

In the present invention, the acrylic resin particles have a functional group of 7 to 330 mmol / 1 per particle weight.
The acrylic resin particles are preferably contained at a concentration of 00 g. Particularly, the acrylic resin particles include a core of a resin component mainly composed of a (meth) acrylic acid ester unit and an acrylic resin component having a functional group-containing monomer unit. Best consists of a shell.

The cross-linking agent may be at least partially soluble in the plasticizer, preferably most of it, and may be reactive with the functional groups in the acrylic resin.
A liquid epoxy compound, a modified or unmodified polyamine, a modified or unmodified polyamidoamine, a methylolated or ether methylolated amino resin, and the like are preferably used.

The plasticizer used is a main plasticizer contained in the plasticizer in an amount of 60% or more and having a molecular weight of 220 to 420.
And the solubility index (SP value) is 7.9 to 10.0.
Those having the above range are excellent in pot life, gelling performance and mechanical performance.

[0014]

In the present invention, as the acrylic resin particles to be dispersed in the dispersion medium mainly containing a plasticizer, a carboxyl group,
Acrylic resin particles having a functional group selected from the group consisting of a salt group, a hydroxyl group, an epoxy group, a methylol group and an etherified methylol group are used, while a dispersion medium having reactivity with the functional group is used. A plasticizer containing the cross-linking agent which is contained in the dispersion medium in a state of being at least partially solubilized is used.

The above-mentioned functional groups present in the acrylic resin prevent the acrylic resin and the plasticizer from being compatible with each other during storage at room temperature, thereby extending the pot life,
It also prevents the acrylic resin from dissolving in the plasticizer to improve the fluidity and workability during coating or molding, and at the time of heat gelation, it reacts with the crosslinking agent in the dispersion medium. As a result, a network cross-linked structure is formed in the resin coating or the molded body, and the creep resistance of this is remarkably improved.

A graph showing the relationship between the elapsed time and the relaxation rate at each heating temperature of Example 1 and Comparative Examples 1 and 2 and gelled acrylic resin described later (FIGS. 1 and 2).
Please refer to. When the entire acrylic resin is formed of a homopolymer of (meth) acrylic acid ester, the pot life is only about two days, but the core of the resin of this (meth) acrylic acid ester unit is When a shell of a resin containing a polar group-containing monomer unit (methacrylic acid) is formed on the surface of, the number of days of pot life is extended to 20 days or longer, particularly 28 days or longer.
Moreover, when the homo-acrylic resin is used (Comparative Example 1) or when the copolymer resin particles having the core-shell structure are used but the crosslinking agent is not added to the dispersion medium (Comparative Example 2). When the elapsed time exceeds a certain limit, the stress relaxation rate suddenly increases, the stress relaxation occurs within 5 minutes at 120 ° C., and the fracture occurs within 10 minutes. When a combination of the acrylic resin particles introduced with and a plasticizer containing a crosslinking agent is used, a stress relaxation time of 1 hour or more is shown at the same temperature.

The reason why a liner or the like made from a vinyl chloride resin plastisol is excellent in creep resistance, while a liner or the like made from an acrylic resin plastisol is inferior in creep resistance is that in the former case, it is dissolved in a plasticizer during gelation. The amorphous portion and the crystalline portion which are not dissolved in the plasticizer have a network structure and exhibit rubber-like elasticity and creep resistance. This is probably because it is crystalline and compatible with the plasticizer, and no network structure is formed. On the other hand, in the acrylic resin plastisol of the present invention, the functional group in the acrylic resin during gelation and the crosslinking agent in the dispersion medium react to generate a network structure, which is a factor that prevents stress relaxation. It seems that has become.

In the present invention, as the acrylic resin particles dispersed in the plasticizer-crosslinking agent dispersion medium, a core of a resin component mainly composed of (meth) acrylic acid ester units, a carboxyl group, a salt group thereof and a hydroxyl group are used. Further advantageous advantages are achieved by using an acrylic resin shell having a functional group selected from the group consisting of epoxy group, epoxy group, methylol group and etherified methylol group.

That is, in the particles having this structure, the functional group (polar group) in the resin is concentrated on the surface, so that the acrylic resin and the plasticizer are compatible with each other during storage at room temperature. The ability to prevent is extremely high. On the other hand, the (meth) acrylic acid ester forming the core is compatible with the plasticizer when heated and gives good gelling performance. Moreover, during this gelation, the functional groups on the surface of the resin particles react quickly and effectively with the crosslinking agent in the dispersion medium to form a crosslinked structure, so that creep resistance and rubber-like elasticity are effectively expressed. Is.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 3 for schematically illustrating the plastisol dispersion structure of the present invention, this plastisol comprises a dispersion medium 4 and acrylic resin particles 1 dispersed therein. . The acrylic resin particles 1 are
It is selected from the group consisting of a resin core 2 mainly composed of a (meth) acrylic acid ester unit and an acid group, a salt group thereof, a hydroxyl group, an epoxy group, a methylol group and an etherified methylol group formed on the surface thereof. And a resin shell 3 having a polar group-containing monomer unit. On the other hand, the dispersion medium is composed of a plasticizer and a cross-linking agent which is dispersed in a state in which at least a part thereof is dissolved.

The core 2 is produced by emulsion polymerization, seed polymerization, suspension polymerization or heterogeneous solution polymerization of a monomer mainly composed of (meth) acrylic acid ester, but the shell 3 is integrated by these polymerization steps. It may be formed by polymerization or may be formed separately.

[Acrylic resin] As the ester of acrylic acid or methacrylic acid, which is the main component of the acrylic resin,
For example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, (meth)
N-Butyl acrylate, isobutyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) Examples include n-octyl acrylate. However, the above-mentioned (meth) acrylic acid means acrylic acid or methacrylic acid. The above (meth) acrylic acid esters may be used alone or in combination, and may be a copolymer with another monomer. The preferred ester is methyl methacrylate. Examples of other comonomers copolymerized with these monomers include styrene, vinyltoluene, acrylonitrile, methacrylonitrile, and vinyl acetate.

When the acrylic resin has a core-shell structure, the content of the (meth) acrylic acid ester unit in the core resin component is 50% by weight or more, particularly preferably 50% by weight, per the core resin component in view of mechanical properties. It is preferably present in an amount of 70% by weight or more.

On the other hand, the monomer component giving the reactive functional group has a carboxyl group, a salt group thereof, a hydroxyl group, an epoxy group, a methylol group or an etherified methylol group. There are things. Ethylenically unsaturated carboxylic acid or its anhydride; acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride and the like. These acid group-containing monomer units may be present in the form of metal salts such as sodium, potassium and calcium, ammonium salts, amine salts and the like.

Examples of the hydroxyl group-containing monomer unit include vinyl alcohol, (meth) acrylic acid hydroxyalkyl ester, particularly (meth) acrylic acid hydroxyethyl ester and (meth) acrylic acid hydroxypropyl ester.

Examples of the epoxy group-containing monomer include (meth) acrylic acid glycidyl ether, allyl glycidyl ether, and butadiene monoxide.

As the monomer having a methylol group and an etherified methylol group, a dimethylol compound of (meth) acrylamide or an ether compound thereof such as an ethyl ether compound or a butyl ether compound is used.

These functional group-containing monomers can be present in the acrylic resin in the form of a random copolymer, a graft copolymer or a block copolymer. It is also acceptable for it to be present in the form of a homopolymer, provided that the entanglement between the polymer chains is sufficient.

As already pointed out, the proportion of the functional group-containing monomer component in the acrylic resin particles is selected from the group consisting of the above-mentioned carboxyl group, its salt group, hydroxyl group, epoxy group, methylol group and etherified methylol group. The polar group may be contained at a concentration of 7 to 330 mmol / 100 g, particularly 15 to 220 mmol / 100 g per particle weight. When the concentration of the polar group is lower than the above range, the pot life is lower than that in the above range, and most importantly, the creep resistance is lower than that in the above range. Become. On the other hand, if the concentration of the polar group exceeds the above range, the gelling performance will be lower than that in the above range.

When the acrylic resin particles have a shell-core structure and the content ratio of the functional group (polar group) -containing monomer unit in the shell is high, the crosslinking reaction between the resin particles and the crosslinking agent is rapid and efficient. In addition, the thickness of the shell, that is, the ratio of the total number of particles can be reduced, so that the adverse effect of the polar group on the gelling performance is reduced. In this sense
The functional group-containing monomer component is preferably composed of a homopolymer or a homopolymer block of the functional group-containing monomer.

The acrylic resin particles should have a molecular weight sufficient to form a tough film, generally 1
It is desirable to have a molecular weight of at least 0,000, especially at least 200,000. The acrylic resin particles have a median particle diameter (median diameter) of 0.1 to 20 μm, particularly 0.3 to 10 μm.
It should be in the range of m. Use of a value obtained by multiplying the number of millimoles of polar groups per 100 g of resin by the particle size (number of μm) is useful for providing a plastisol having a well-balanced pot life and gelling performance, regardless of the particle size. It was found that the conditions for various resin particles can be specified. Particle size (μm) in millimoles of carboxylic acid per 100 g of resin
When a value multiplied by a number is expressed as BF, the BF of the resin particles is preferably in the range of 2 <BF <200, more preferably 7 <, in order to obtain a plastisol having excellent pot life and gelling performance. Adjusting to a range of BF <150 gives very good results. In addition, it is KB to decide BF
Resin 100 determined by IR measurement by the diffuse reflection method under the condition that r powder and resin powder were uniformly mixed at a ratio of 95: 5.
The mmoles of carboxylic acid per g are used. Diffuse reflection I
When the R method is used, the information in the vicinity of the surface of the particle can be selectively taken out, so that the amount of carboxylic acid in the particle shell part can be determined.

[Production of Acrylic Resin] Acrylic resin particles used in the present invention are obtained by emulsion polymerization of a monomer mainly composed of (meth) acrylic acid ester and a functional group-containing monomer.
It is produced by polymerization by suspension polymerization, heterogeneous solution polymerization, seed polymerization, graft polymerization or the like. In these polymerizations, if the functional group-containing monomer is added in the latter-stage polymerization, particles having the functional group-containing monomer component as a shell are produced. In addition, a shell rich in the functional group-containing monomer component can also be formed by subjecting the acrylic resin once produced to saponification or other chemical treatment. .

The production of acrylic resin particles is generally carried out by emulsifying or suspending each of the above components as an oil phase in water and carrying out emulsion polymerization or suspension polymerization in the presence of a polymerization initiator.
The aqueous medium is preferably used in an amount of 0.6 to 4 times by weight, particularly 1 to 2.3 times by weight, based on the total amount of the above monomer components.

In emulsion polymerization, the dispersion particle size of the monomer in water is controlled to an emulsion particle size, generally 0.05 to 0.2 μm, by a surfactant, particularly an anionic surfactant or a nonionic surfactant. And polymerize. The amount of the surfactant used is appropriately 0 to 5 parts by weight based on 100 parts by weight of the monomer component.

At the time of suspension polymerization, it is preferable to adjust the particle size of the dispersed phase in the range of 1 to 20 μm by using an ordinary suspension stabilizer. Examples of the suspension stabilizer include water-soluble polymers, poorly water-soluble powdered inorganic compounds, surfactants and the like known in the art. Examples of the water-soluble polymer include gelatin, tragacanth gum, starch, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid salts and the like. Examples of the inorganic compound include barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, calcium phosphate, talc, bentonite, diatomaceous earth and clay. The amount of the suspension stabilizer used is usually 0.1 to 5 parts by weight per 100 parts by weight of the suspended particles. The emulsification or suspension of the oil phase in the emulsification or suspension polymerization method is performed by a normal low and medium shear stirrer, or by a high shear stirrer such as a homomixer and a homogenizer, and the core particles are sized according to the purpose. The diameter can be adjusted.

As the polymerization initiator, in the case of suspension polymerization, for example, azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethyl). Azo compounds such as valeronitrile),
Cumene hydroperoxide, dicumyl peroxide, t
-Oil-soluble initiators such as butyl hydroperoxide, di-t-butyl peroxide, benzoyl peroxide, and peroxides such as lauroyl peroxide are used, and in the case of emulsion polymerization, for example, hydrogen peroxide solution, potassium persulfate, Water-soluble initiators such as ammonium persulfate, azobiscyanovaleric acid, azobisisobutylamidine hydrochloride are used. Further, the peroxide type initiator can be used as a redox type low temperature initiator in combination with a suitable reducing agent. In addition to these, a combination of ionizing radiation such as γ-ray or accelerated electron beam or ultraviolet ray and various sensitizers can be used. The polymerization initiator is preferably used in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the monomer. The polymerization is usually carried out in an inert atmosphere such as nitrogen at a temperature of 50 to 100 ° C. for about 2 to 12 hours.

The production of acrylic resin particles can also be carried out by heterogeneous solution polymerization. In this polymerization method, a solvent that dissolves the monomer but does not dissolve the produced polymer,
For example, alcohol is used, the monomer is dissolved in a solvent, and the polymerization is carried out in the presence of a polymerization initiator. In this case,
As the polymerization proceeds, particle growth of the produced polymer occurs and desired resin particles are obtained. The particle size of the acrylic resin particles and the core-shell structure can be adjusted by seed polymerization. For example, resin particles obtained by emulsion polymerization can be dispersed in an aqueous medium, a monomer and an initiator can be added, and polymerization on the surface of seed particles can be performed.

In order to form a shell having a carboxyl group, a hydroxyl group or other polar group on the surface of the core particle, the following means are adopted.

(1) Saponification method If acrylic acid ester, methacrylic acid ester, or vinyl acetate is present in at least the outermost shell, the particles are polymerized in water (emulsion polymerization, seed polymerization, suspension polymerization) and then hydroxylated. By heating in the presence of a strong alkali such as sodium to hydrolyze or saponify the ester,
A carboxyl group or a hydroxyl group can be easily introduced on the outermost surface of the particles. Since the thickness of the material layer incompatible with the plasticizer can be minimized, the influence on the physical properties of the gel can be minimized.

(2) Emulsion and Seed Polymerization Method It is difficult to polymerize a water-soluble monomer such as acrylic acid or methacrylic acid and introduce it into particles by ordinary underwater polymerization. By making the anionic monomer acidic and making the cationic monomer alkaline, and by adding a non-solvent for these monomers, the water solubility of the monomers is reduced, and they are fixed on the particle surface to allow polymerization. It can be done. It is also possible to make the outermost layer rich in polar monomers by devising a monomer feed, that is, by adding a polar monomer in the polymerization system in a single step or multiple steps together with an initiator as needed during the polymerization. is there. In emulsion polymerization, the polar monomer tends to gather in the outermost shell and the hydrophobic monomer tends to gather in the inner shell, so that it is relatively easy to control the core / shell structure. The polymerization conditions may be those already mentioned.

[Crosslinking Agent] The crosslinking agent to be present in the plasticizer is a resin component which is reactive with the functional groups in the acrylic resin and is at least partially soluble in the plasticizer. Is used. Those having an amino group, a hydroxyl group or an epoxy group for the carboxyl group of the acrylic resin or its salt group, and those having a carboxyl group, an epoxy group, a methylol group or an etherified methylol group for the hydroxyl group A carboxyl group for an epoxy group, a salt group thereof, a hydroxyl group, an amino group, a methylol group or an etherified methylol group, a carboxyl group for a methylol group and an etherified methylol group, a salt group thereof, Those having a hydroxyl group, an epoxy group, a methylol group and an etherified methylol group are used.

A liquid epoxy compound, a modified or unmodified polyamine, a modified or unmodified polyamidoamine, a methylolated or ether methylolated amino resin, or the like is preferably used as such a curing agent resin component. These may be used alone or in combination of two or more, or may be used in combination with other curing aid or curing catalyst.

The liquid epoxy compound has 2 in the molecule.
A liquid epoxy compound having at least one oxirane ring, particularly an epoxy resin is used. Among them, bisphenol A is used.
Suitable are bisphenol A type epoxy resins obtained by polycondensation of bisphenols such as epihalohydrin with an epoxy equivalent of generally 100 to 500, particularly 150 to 300, and a number average molecular weight of 250.
It is preferably in the range of 1000 to 1000, particularly 300 to 700.

As the modified polyamine, a primary one in the molecule,
Among aliphatic, alicyclic or aromatic compounds having a large number of secondary or tertiary amino groups, those satisfying the above conditions are used, and examples thereof include polyalkylene polyamine, polyethylene imine, polyvinyl amine and the like. , Their fatty acids, rosins, phenolic resins, epoxy resins,
And the like are used. A modified product is preferable in terms of solubility in a plasticizer. As the modified polyamidoamine, a low molecular weight aliphatic polyamide having a large number of primary, secondary or tertiary amino groups in the molecule, for example, a reaction product of a fatty acid dimer (dimer acid) and a diamine or the above polyamine And the like, and modified products thereof with fatty acids, rosins, phenol resins, epoxy resins and the like are used. A modified product is preferable in terms of solubility in a plasticizer.

Examples of the methylolated or ether methylolated amino resin include urea resin, melamine resin and benzoguanamine resin having a large number of methylol groups in the molecule. As the ether type resin, a resin obtained by etherifying the ether group of the above resin with an alcohol such as ethanol or butanol is used.

[Plastisol composition] The plastisol composition of the present invention comprises a dispersion medium comprising a plasticizer for acrylic resin and a crosslinking agent at least partially dissolved in the plasticizer.
Surface-polarized acrylic resin particles dispersed in this dispersion medium.

As the plasticizer, esters of aromatic dibasic acids or polybasic acids such as phthalic acid; esters of aliphatic dibasic acids or polybasic acids; phosphoric acid esters; hydroxy polycarboxylic acid esters; Among fatty acid esters, polyhydric alcohol esters, and epoxidized oils, those suitable for acrylic resins are used.

A preferred plasticizer is a main plasticizer having a molecular weight of 220 to 4 contained in the plasticizer in an amount of 60% by weight or more.
20 and a solubility index (SP value) of 7.9 to 1
It is in the range of 0.0. Here, the solubility index (Solub
It is widely used as a standard for evaluating the compatibility of substances, and the SP value is defined by J. BRANDRU
P etc. Polymer Handbook (1967
Year) As defined in Chapter 4, it is a 1/2 power value of the cohesive energy density and represents the degree of hydrogen bonding of a substance. When the degree of hydrogen bonding is large, it takes a large value.

The aromatic acid constituting the plasticizer may be phthalic acid, the aliphatic carboxylic acid may be adipic acid, azelaic acid or sebacic acid, and the hydroxycarboxylic acid may be glycolic acid. To be As the alkyl group in the ester, a lower alkyl group such as ethyl, propyl and butyl is used, and within a range satisfying the above molecular weight, a higher alkyl group such as isodecyl group, octyl group (ethylhexyl group), benzyl group or cresyl group is used. Those having an aralkyl group such as a group are also used.

Specific examples thereof include diethyl phthalate, dibutyl phthalate, butylbenzyl phthalate, acetyltributyl citrate, butylphthalyl glycolate, dioctyl adipate and dioctyl phthalate.

The weight ratio of the acrylic resin particles to the plasticizer is such that sufficient fluidity can be obtained during coating and molding, and sufficient physical properties can be obtained during gelation. The amount is preferably 50 to 120 parts by weight, particularly 60 to 100 parts by weight, per 100 parts by weight of the resin particles.

On the other hand, the weight ratio of the acrylic resin particles to the cross-linking agent varies depending on the respective concentrations of the functional groups involved in the cross-linking reaction, but generally speaking, per 100 parts by weight of the acrylic resin particles. It is preferably in the range of 1 to 30 parts by weight, particularly 2 to 20 parts by weight. If the amount ratio of the cross-linking agent is less than the above range, the degree of cross-linking of the acrylic resin particles is lowered, and sufficient creep resistance tends to be unobtainable. On the other hand, if the amount ratio of the crosslinking agent is more than the above range,
There is an inconvenience that the fluidity at the time of coating and molding is lowered, or the hardness of the gelled product becomes too high, so that the cushioning property and the flexibility are lost.

The plastisols include resin compounding agents known per se, such as fillers, colorants, heat stabilizers, foaming agents, crosslinking agents, antioxidants, thickeners, thickeners, oxygen absorbers and the like. Can be compounded according to a formulation known per se.

[Use] The acrylic resin plastisol composition of the present invention has an excellent pot life and gelation performance, and the obtained coating or molded article has excellent creep resistance. Therefore, PVC plastisol can be widely used for various applications where it has been widely used in the past, such as packing or gaskets, interior parts, toys, daily necessities, miscellaneous goods, various coatings, various backings, and films or sheets.

For the molding, means such as slush molding, rotational molding, casting, dip molding, etc. can be used, and for coating, spread method, depping method, spin coating method, gravure coating method, spray coating method, A screen coating method or the like is adopted. The acrylic resin plastisol of the present invention is particularly useful for forming a gasket or a liner for sealing various containers and container lids by spin coating.

Generally, the acrylic resin plastisol composition of the present invention preferably has a viscosity of 0.5 to 1000 poise at room temperature from the viewpoint of workability during coating and molding,
On the other hand, the hardness at the time of gelation varies depending on the application, but it is 1 for the applications such as the above-mentioned sealing gasket or liner.
It preferably has a hardness (JIS-A) of 5 to 75. The plastisol can be easily cured by heating it to a temperature of 100 to 230 ° C.

[0057]

The invention is explained in more detail in the following examples. Description of curing agent Cymel 325: melamine-based curing agent manufactured by Mitsui Cyanamid Co., Ltd. Cymel 1123: benzoguanamine-based curing agent manufactured by Mitsui Cyanamid Co., Ltd. Adeka EH203: modified polyamidoamine-based curing agent Adeka EH331: modified polyamidoamine-based system manufactured by Asahi Denka Co., Ltd. The abbreviations in the curing agent examples have the meanings given in Table 1 below.

[0058]

[Table 1]

Example 1 Using sodium dodecylbenzene sulfonate as an emulsifier and potassium peroxodisulfate as an initiator, methyl methacrylate (MMA) / glycidyl methacrylate (GMA) weight was measured by a conventional emulsion polymerization method and seed polymerization method. A copolymer resin particle dispersion having a ratio of 95/5 was prepared. When the particle size was measured by Microtrac, the average particle size was 1.8 μm. To this dispersion, 4 parts by weight of sodium hydroxide per resin component was added, and hydrolysis was carried out under conditions of 95 ° C. for 5 hours to prepare core / shell particles. The reaction mixture was neutralized with an equal amount or more of a dilute hydrochloric acid aqueous solution, the solid content was suction filtered, and then dried in an electric oven at 90 ° C. to prepare a reactive copolymer resin powder.

The particles prepared here have a glycidyl group and a carboxyl group as reactive functional groups, and the molecular weight of the resin can be determined to be 1.8 million by GPC measurement using tetrahydrofuran (THF) as a solvent. It was still,
By the diffuse reflection IR measurement, the number of millimoles of carboxylic acid was 21 millimoles and the BF was 38 per 100 g of the resin.

In a mortar, 40 parts of BPBG as a plasticizer,
2 parts Epicoat 828 as crosslinker, Cymel 703
1.3 parts and 0.1 parts of Catalyst 6000 were charged and mixed with a pestle to uniformly dissolve. The Epicoat 828 used here is a liquid epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., which is Cymel 703 and Catalyst 60.
00 is a melamine resin and a curing catalyst manufactured by Mitsui Cyanamid Co., Ltd., respectively. The Cymel 703 obtained had a solid content of 80% and the rest was butanol.

To the above homogeneous solution of the plasticizer and the cross-linking agent, 50 parts of the reactive copolymer resin powder prepared previously was added,
A uniform transparent plastisol was prepared by kneading with a pestle. After defoaming in a vacuum dryer, spread each on an aluminum plate and a tin plate with a knife coater to a thickness of about 1 mm,
Heat treatment for 3 minutes in a 180 ° C hot-air circulating electric oven,
A gelled sheet was prepared. The sample sheet gelled on the aluminum plate was completely bonded to the aluminum plate and could not be peeled off from the plate. The gelled sheet peeled from the tin plate was flexible, and a sample piece having a thickness of about 1 mm cut into a width of 7 mm was so strong that it could not be torn by hand at room temperature. In the hardness measurement, JIS-A hardness is 6
0 was shown.

Creep resistance test (stress relaxation measurement) Creep resistance was evaluated by stress relaxation measurement. The stress relaxation property and the creep property are in a one-sided relationship. Specifically, a sample piece with a width of 7 mm and a thickness of about 1 mm is sandwiched between two chucks, upper and lower, and a tensile strain of 50% is instantaneously applied to the sample, and the stress is relaxed with time from the moment the strain is applied to the sample. I observed how it was going. When the temperature was 120 ° C., the measurement was performed for about 1 hour.

The stress 0.1 second after the strain is applied is defined as the initial stress σ.
0 and the stress after t time is σt, σt / σ0 is e
The time t when -1 (= 0.368) was defined as the relaxation time. In order to provide a sealing gasket that does not undergo creep deformation during use as a sealing gasket, retains excellent sealing properties for a long time, and can be applied to applications requiring heat resistance, The relaxation time must be at least 10 minutes or longer. Incidentally, 120
In the case where the sample is broken at the measurement of 1 ° C for 1 hour, it cannot be used as a sealing gasket. As a result of stress relaxation measurement, the relaxation time at 120 ° C is 1
It was not possible to measure it over the time, and no breakage of the sample was observed during the measurement.

Test of Sealability A white cap shell having a diameter of 53 mm was lined with the plastisol composition and heat-treated at 180 ° C. for 3 minutes to gel the plastisol to form a liner portion. Put 150 g of water in a thick glass bottle with an internal volume of 225 ml, seal with a white cap, and leave at 110 ° C-
The retort treatment was performed for 60 minutes, and the weight change before and after the retort was observed. The sealing was performed under the condition that the liner was subjected to compressive strain of 40%. As a result, no weight change was observed before and after the retort, and it was confirmed that the hermeticity was maintained under the retort conditions. Further, no visual damage was observed on the liner portion.

Evaluation of pot life The pot life of plastisol was evaluated based on the viscosity measurement data. A B-type viscometer was used for viscosity measurement, and No.
It was carried out under the conditions of 4 rotors, 6 rotations, and 25 ° C. The number of days of storage when the viscosity value exceeded 1000 poises was used as a measure of pot life. In order to produce a practically useful plastisol, the pot life here is preferably 20 days or longer. Viscosity measurement is carried out for up to 4 weeks, and if the viscosity still does not reach 1000 poise after 4 weeks,
The pot life was displayed as> 28. Evaluation result is> 2
It was stable at 8.

Comparative Example 1 The plastisol composition of Example 1 without the crosslinking agent was prepared, and the same evaluation as in Example 1 was measured. In the stress relaxation measurement, the relaxation time at 120 ° C. was 5 minutes, and it was confirmed that the creep resistance was inferior because the sample broke 8 minutes after the start of the measurement. In the sealability test, it was confirmed that there was a weight change of 10 g before and after the retort, and from the visual observation of the liner part,
It was found that the liner had fine cracks. From this comparative example, it is understood that the crosslinking agent is an essential component in order to provide a plastisol composition excellent in creep resistance and sealing property. In addition, the evaluation of the plastisol pot life was the same as in the example.

1 and 2 show the results of stress relaxation measurement of Example 1 and Comparative Example 1, respectively. It is a plot of relaxation elastic modulus Er (t) (dyn / cm ² ) against time t (seconds), and stress relaxation measurement was performed at 90 ° C. and 120 ° C.
It is the result of carrying out at ° C. From these figures, it is clear that the composition of Example 1 has excellent creep resistance.

Comparative Example 2 For comparison with Example 1,
MMA homopolymer particle powder was prepared under the same polymerization conditions as in Example 1. The molecular weight and particle size were 2 million and 1.8 μm, respectively. Resin particles from reactive copolymer to M
The same composition as in Example 1 except that the MA homopolymer was used,
A plastisol composition was prepared under the same conditions and evaluated for creep resistance, hermeticity and pot life.

In the stress relaxation measurement, the relaxation time at 120 ° C. was 4 minutes, and the sample broke 4 minutes after the start of the measurement, which confirmed that the creep resistance was inferior. Even in the sealability test, the weight change before and after the retort and the occurrence of cracks in the liner were confirmed, and the plastisol prepared from the non-reactive polymer particles produced a sealing gasket with excellent creep resistance and sealability. It turns out that I can't. In other words, it can be said that the reactive polymer particles are an essential component for providing a plastisol composition having excellent creep resistance and sealing property. The pot life was evaluated as 2 days and the storage stability was also poor.

[Comparative Example 3] In Comparative Example 3, the examination result when the curing agent component of Example 1 is changed is shown. 40 parts of BPBG as a plasticizer and Epicoat 82 as a curing agent
8 parts and 2 parts, 2 parts of tetramethylolated bisphenol A (phenol resin A) obtained from Toyo Ink Mfg. Co., 2 parts were premixed, and further 50 parts of the reactive copolymer resin powder used in Example 1 was added. A plastisol composition was prepared by combining the above. Phenolic resin A was obtained in the form of a 50% solids butanol solution. It was confirmed that by premixing the phenol resin A and the plasticizer, the liquid became cloudy and a dispersion of the phenol resin A was formed, and the phenol resin A was not compatible with the plasticizer.

As a result of evaluation of creep resistance and sealability, a sudden breakage occurred 5 minutes after the start of measurement in the stress relaxation measurement, and in the sealability test, the change in weight before and after the retort and the damage of the liner part were observed. confirmed. As a result,
It was found that when the curing agent component and the plasticizer are not compatible with each other, the uniform crosslinking reaction does not proceed and the curing agent blending effect is not exhibited.

[Embodiment 2] Furthermore, in Embodiment 2, Embodiment 1
The examination results when the curing agent component of is changed are shown below.
40 parts of BPBG as a plasticizer, 2 parts of Epicoat 828, 1 part of ADEKA HARDNER 6302, 0.2 part of ADEKA HARDNER EH252 as a curing agent were premixed, and further the reactive copolymer resin used in Example 1 was used. A plastisol composition was prepared in combination with 50 parts of powder. Adeka Hardener is a curing agent manufactured by Asahi Denka Co., Ltd., 6302 is a modified polyamidoamine, and EH252 is a modified aliphatic polyamine. All were obtained in the form of liquids having 100% resin content. The compatibility between ADEKA HARDNER 6302 and BPBG was poor and it did not completely dissolve, but the colorless and transparent BPBG was strongly colored, and ADEKA HARDNER 6302 was BPB.
It was confirmed that G was partially solubilized.

As a result of evaluation of creep resistance and hermeticity, the stress relaxation measurement showed that the relaxation time at 120 ° C. was 1 hour or longer, and no fracture was observed. Also, in the sealability test, there was no change in weight before and after the retort, and the liner was not damaged. From the results of Example 2, it was confirmed that if the curing agent was partially solubilized in the plasticizer, the curing agent was sufficiently cured.

[Examples 3 to 10 and Comparative Examples 4 to 10] In Examples 3 to 10 and Comparative Examples 4 to 10, the composition of the reactive copolymer resin particles, the resin molecular weight, the particle diameter, the type of the plasticizer, Various plastisol compositions having different compositions and amounts of the cross-linking agent were prepared and evaluated for creep resistance and sealing property in the same manner as in Example 1. Details of resins, plasticizers, curing agents and the like used in Examples and Comparative Examples are shown in Table 2 and described.

[0076]

[Table 2]

Table 2 also shows the gelling performance when a small amount of plastisol sample was placed in an aluminum pan and heat-treated at 180 ° C. for 3 minutes. ○ When a flexible and tough gelled sheet was obtained, △, when the sheet was a flexible sheet but the strength was slightly reduced, ×, when it was not a flexible sheet
Displayed in. Then, the creep resistance test and the sealability test were performed only on the plastisol composition from which the flexible sheet was obtained. The evaluation results are described in Table 3.

[0078]

[Table 3]

[Example 11] Sodium dodecylbenzenesulfonate as an emulsifier and peroxo-2 as an initiator
Using potassium sulfate, by emulsion polymerization method and seed polymerization method,
Methyl methacrylate (MMA) / methacrylic acid (MA
A) A copolymer resin dispersion having a weight ratio of 90/10 was prepared. At this time, after homopolymerizing 3/4 amount of MMA,
Polymerization was carried out by using a 1/4 amount of A and the total amount of MAA and carrying out a multistage feed in which the MMA / MAA ratio was successively increased. In the particle size measurement by Microtrac, a value of an average particle size of 1.6 μm was obtained. This dispersion was spray dried and further dried under reduced pressure at 90 ° C. or lower to prepare a completely dried reactive copolymer resin powder.

The molecular weight of the resin was determined to be 2.3 million by GPC measurement using THF as a solvent. Incidentally, from the diffuse reflection IR measurement, the number of millimoles of carboxylic acid per 100 g of the resin could be determined to be 82 millimoles and BF131.

50 parts of the above reactive resin powder, ATBC40
Section, 4 pieces of Epicoat 828, 2.5 pieces of Cymel 703
Parts and 0.2 parts of catalyst 6000 to prepare a plastisol paste, and in the same manner as in Example 1,
The creep resistance, sealing property, and pot life were evaluated.

In the creep resistance test, the relaxation time at 120 ° C. was 1 hour or longer, and no breakage of the sample was observed during the relaxation measurement. In the sealing test, there was no change in weight before and after the retort, and no damage was observed on the liner. The pot life was> 28 days and was very stable.

[0083]

EFFECTS OF THE INVENTION According to the present invention, acrylic resin particles dispersed in a dispersion medium containing a plasticizer as main components include carboxyl groups, salts thereof, hydroxyl groups, epoxy groups, methylol groups and etherified methylol groups. While using acrylic resin particles having a functional group selected from the group consisting of,
As a dispersion medium, by using a plasticizer containing a cross-linking agent having reactivity with the functional group in the dispersion medium at least partially solubilized, even during long-term storage, coating, molding, etc. The excellent fluidity required for
It was possible to provide an acrylic resin plastisol which exhibits excellent gelation performance upon heating and which has a significantly improved creep resistance in the obtained coating or molded article.

That is, the above-mentioned functional groups present in the acrylic resin prevent the acrylic resin and the plasticizer from compatibilizing each other at the time of storage at room temperature to prolong the pot life. Acrylic resin is prevented from dissolving in the resin to improve fluidity and workability during coating and molding, and at the time of heat gelation, it reacts with the cross-linking agent in the dispersion medium to form a resin coating. Or, a network cross-linking structure is formed in the molded product, and the creep resistance of this product is remarkably improved.

Since this acrylic resin plastisol has various performances comparable to those of vinyl chloride homopolymers and copolymer plastisols, it prevents the release of hydrogen chloride into the atmosphere and the generation of dioxins during incineration, and There are significant advantages.

[Brief description of drawings]

1 is a result of stress relaxation measurement of Example 1, showing relaxation elastic modulus Er (t) (dyn / cm) with respect to time t (seconds).
It is a graph in which ² ) is plotted.

FIG. 2 is a result of stress relaxation measurement of Comparative Example 1, showing relaxation elastic modulus Er (t) (dyn / cm) with respect to time t (seconds).
It is a graph in which ² ) is plotted.

FIG. 3 is an explanatory view for schematically explaining the plastisol dispersion structure of the present invention.

[Explanation of symbols]

 1 Acrylic Resin Particles 2 Acrylic Resin Core 3 Shell Made of Functional Group-Containing Monomer Component 4 Dispersion Medium

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 19, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0085

[Correction method] Change

[Correction content]

Since this acrylic resin plastisol has various performances comparable to those of vinyl chloride homopolymers and copolymer plastisols, it prevents the release of hydrogen chloride into the atmosphere and the generation of dioxins when incinerated, and There are significant advantages.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

1 is a result of stress relaxation measurement of Example 1, showing relaxation elastic modulus Er (t) (dyn / cm) with respect to time t (seconds).
It is a graph in which ² ) is plotted.

FIG. 2 is a result of stress relaxation measurement of Comparative Example 1, showing relaxation elastic modulus Er (t) (dyn / cm) with respect to time t (seconds).
It is a graph in which ² ) is plotted.

FIG. 3 is an explanatory view for schematically explaining the plastisol dispersion structure of the present invention.

[Description of Reference Signs] 1 acrylic resin particles 2 core of acrylic resin 3 shell 4 composed of functional group-containing monomer component 4 dispersion medium

Claims (6)

[Claims] 1. A plastisol composition comprising a dispersion medium containing a plasticizer as a main component and acrylic resin particles dispersed in the dispersion medium, wherein the acrylic resin particles include a carboxyl group, a salt group thereof, a hydroxyl group, and an epoxy group. Group, an acrylic resin particles having a functional group selected from the group consisting of a methylol group and an etherified methylol group, and the dispersion medium at least a crosslinking agent having reactivity with the functional group in the dispersion medium. An acrylic plastisol composition having excellent creep resistance, which is contained in a partially solubilized state. 2. The plastisol composition according to claim 1, wherein the acrylic resin particles contain the functional group in a concentration of 7 to 330 mmol / 100 g per particle weight. 3. The acrylic resin particle, wherein the acrylic resin particle comprises a core of a resin component mainly composed of a (meth) acrylic acid ester unit, and a shell of an acrylic resin component having the functional group-containing monomer unit. Claim 1
The described plastisol composition. 4. The plastisol composition according to claim 1, wherein the crosslinking agent is a liquid epoxy compound, a modified or unmodified polyamine, a modified or unmodified polyamidoamine, or a methylolated or ether methylolated amino resin. 5. The main plasticizer contained in the plasticizer in an amount of 60% by weight or more has a molecular weight of 220 to 420 and a solubility index (SP value) in the range of 7.9 to 10.0. The plastisol composition according to claim 1, which is a plasticizer. 6. The plastisol composition according to claim 1, wherein the crosslinking agent is present in an amount of 1 to 30 parts by weight and the plasticizer is present in an amount of 50 to 120 parts by weight, based on 100 parts by weight of the acrylic resin particles.