JP2004196909A - Heat-sealing material for easily openable container and easily openable container using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sealing material for an easily openable container which has sufficient sealing strength even by heat sealing at low temperatures and, simultaneously, can form a heat-sealed portion easy to open on opening, and an easily openable container. <P>SOLUTION: The heat-sealing material for an easily openable container comprises a modified propylene polymer obtained by subjecting 30-95 wt.% crystalline propylene polymer which satisfies condition (1) of a melting point [T<SB>m</SB>(°C)], measured by a differential scanning calorimeter, of 110-160°C, condition (2) of a ratio [M<SB>w</SB>/M<SB>n</SB>] of the weight average molecular weight [M<SB>w</SB>] to the number average molecular weight [M<SB>n</SB>] of 2.5-4.0, and condition (3) of a growth rate [S(μm/sec)] of the spherulite radius having the relationship of formula (Ia): 0.140<S, when the solidification treatment temperature is taken as [T<SB>m</SB>-30°C], and 70-5 wt.% vinyl monomer to graft reaction conditions. The easily openable container has a heat-sealed structure in which the heat-sealing material for the openable container and the surface of a propylene resin are heat-sealed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５５】
【発明の効果】
本発明によれば、低温での熱封着でも充分な封着力を有すると共に、開封時の開封が容易な熱封着部を形成することができる易開封性容器用熱封着材及びそれを用いた易開封性容器を提供することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention uses a heat-sealing material for an easily-openable container, which has a sufficient sealing force even at a low-temperature heat-sealing and can form a heat-sealed portion which can be easily opened at the time of opening, and the same. More particularly, the present invention relates to a heat-sealing material for an easily-openable container suitably used for a packaging container or a packaging bag having a propylene-based resin on a heat-sealing surface, and an easily-openable container using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, seal pack packaging, in which a resin container body is heat-sealed with a resin film-like lid material and packaged, has been widely used mainly for packaging food and beverage products such as dairy products, confectionery, fruit juice beverages, and the like. Together with the bag, it has taken on an important position. As the heat sealing material, a solution-type adhesive or a hot-melt type adhesive has conventionally been used, but these heat-sealing materials cause ductile destruction at the time of opening to form a thread. Therefore, there is a problem that the opening is not always easy, or the peeling surface has a poor appearance, such as poor appearance. Also, due to lack of heat resistance, the sealing property such as peeling at high temperatures. There was a problem that lacked.
[0003]
In order to improve such problems, various heat sealing materials having both sealing properties and easy-opening properties have been proposed and used. For example, there is a composition in which a tackifier is mixed with an ethylene-vinyl acetate copolymer, and a material mainly composed of a modified olefin polymer obtained by modifying an olefin polymer with an aromatic vinyl monomer. (For example, refer to Patent Document 1). Further, a heat sealing material mainly composed of a modified propylene resin obtained by modifying a propylene resin with an aromatic vinyl monomer, the propylene resin such as a packaging container having a propylene resin on a heat sealing surface. An easily-openable container or the like heat-sealed on its surface has also been proposed (for example, see Patent Documents 2 and 3).
[0004]
[Patent Document 1]
Japanese Patent Publication No. 1-42967.
[Patent Document 2]
JP-A-11-100483.
[Patent Document 3]
JP-A-2000-177079.
[0005]
However, examinations by the present inventors have revealed that the easily-openable containers disclosed therein leave room for improvement in heat sealability at low temperatures.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned prior art in a heat-sealing material for an easily-openable container and an easily-openable container. Therefore, the present invention provides a sufficient sealing force even at a low-temperature heat sealing. It is an object of the present invention to provide a heat-sealing material for an easily-openable container which can form a heat-sealing portion which can be easily opened at the time of opening, and an easily-openable container using the same.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the above object can be achieved by using a specific modified propylene-based polymer, and have completed the present invention. Is obtained by subjecting 30 to 95% by weight of a crystalline propylene polymer satisfying the following conditions (1), (2) and (3) and 70 to 5% by weight of a vinyl monomer to a graft reaction condition. A heat-sealing material for an easily-openable container containing the obtained modified propylene-based polymer, and heat-sealing obtained by heat-sealing the heat-sealing material for the easily-openable container and the propylene-based resin surface. An easy-open container having a structure is provided.
[0008]
(1) The melting point [T _m (° C.)] measured by a differential scanning calorimeter is 110 to 160 ° C.
(2) Weight average molecular weight The number average molecular weight of [M _w] ratio [M _n] [M _w / M _n] is from 2.5 to 4.0.
(3) The growth rate [S (μm / sec)] of the spherulite radius when the solidification temperature is [T _m −30 ° C.] has the relationship of the following formula (Ia).
0.140 <S (Ia)
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
As the crystalline propylene-based polymer in the modified propylene-based polymer constituting the heat-sealing material for the easily-openable container of the present invention, a propylene homopolymer, or a copolymer of propylene and another α-olefin The α-olefin other than propylene is usually one having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, specifically, for example, ethylene, 1-butene, 3 -Methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like. Further, the propylene-α-olefin copolymer may be a binary or ternary or higher copolymer, or may be a random or block copolymer. As the propylene-α-olefin copolymer in the present invention, a propylene-ethylene random copolymer, a propylene-ethylene-based copolymer such as propylene-ethylene-other α-olefin random copolymer, or propylene-1- A propylene-1-butene copolymer such as a butene random copolymer is preferred, and a propylene-ethylene random copolymer is particularly preferred.
[0010]
In the crystalline propylene polymer according to the present invention, it is essential that the melting point [T _m (° C.)] measured by a differential scanning calorimeter is 110 to 160 ° C. under the condition (1), and 115 to 150 ° C. C., preferably from 120 to 140C. If the melting point [T _m ] is less than the above range, the heat sealing properties of the heat-sealing material for an easily-openable container will be poor, while if it exceeds the above range, the heat sealing properties at low temperatures will be poor.
[0011]
Furthermore, in the crystalline propylene polymer of the present invention, the ratio [ _Mw / _Mn ] of the weight average molecular weight [ _Mw ] to the number average molecular weight [ _Mn ] under the condition (2) is 2.5 to 4.0. It is essential that it is 0, preferably 2.6 to 3.8, and particularly preferably 2.7 to 3.6. When the ratio M _w / M _n is less than the above range, the heat sealing material at a low temperature is inferior as a heat sealing material for an easily-openable container. . In the present invention, the weight average molecular weight [M _w ] and the number average molecular weight [M _n ] are measured by gel permeation chromatography.
[0012]
Further, in the crystalline propylene-based polymer of the present invention, the growth rate [S (μm / sec)] of the spherulite radius when the solidification temperature is [T _m −30 ° C.] under the condition (3) is as follows: It is essential to have the relationship of the following formula (Ia), preferably the relationship of the following formula (Ib), and particularly preferably the relationship of the following formula (Ic).
[0013]
0.140 <S (Ia)
0.160 <S (Ib)
0.180 <S (Ic)
[0014]
Here, when the crystalline propylene polymer is used as a heat-sealing material for an easily-openable container by a modification described below, fine irregularities generated on the heat-sealing material surface due to the spherulite size are unsealed. When the growth rate of the spherulite radius [S] is less than the above range, the heat sealing property at low temperature is inferior as a heat sealing material for an easily-openable container. It becomes.
[0015]
In the present invention, the growth rate of the spherulite radius [S (μm / sec) is determined by sandwiching the polymer sample between two glass plates provided with a 20 μm-thick aluminum foil as a spacer, and placing the sample on a 200 ° C. hot plate. After heating for 5 minutes to form a sufficiently molten state, the mixture was transferred to a temperature adjusting tank (“TC-600Ph” manufactured by Linkham Inc.), kept at 200 ° C. for 1 minute under a nitrogen atmosphere, and then the temperature of the tank was solidified. The temperature is lowered at a rate of 75 ° C./min to a temperature [T _m −30 ° C.] lower than the melting point [T _m ] of the polymer by 30 ° C. as a treatment temperature, and the crystallization state at the same temperature ± 1 ° C. By observing with a microscope or the like and measuring the spherulite radius with respect to the elapsed time, the growth rate [S (μm / sec)] of the spherulite radius can be obtained.
[0016]
The crystalline propylene polymer satisfying the above conditions (1), (2) and (3) has a melt flow rate of 0 measured at a temperature of 230 ° C. and a load of 21.18 N according to JIS K6921. It is preferably from 0.5 to 200 g / 10 min, more preferably from 1 to 100 g / 10 min, and particularly preferably from 2 to 50 g / 10 min.
[0017]
The method for producing the crystalline propylene-based polymer in the present invention is not particularly limited as long as the conditions (1), (2), and (3) are satisfied, and may be a conventionally known method. For example, typically, a transition metal compound such as a titanium-containing compound, or a carrier-supported compound in which the transition metal compound is supported on a carrier such as a magnum-containing compound is used as a main catalyst, and an organometallic compound such as an organoaluminum compound is used. Ziegler-Natta catalysts as co-catalysts, or, typically, titanium group elements (titanium, zirconium, and zirconium, which are transition metal elements of group 4 of the periodic table containing two bridged conjugated 5-membered ring ligands) Hafnium) as a main catalyst and an ion-exchangeable layered silicate such as montmorillonite, or an organic metal compound such as an organoaluminum compound as a co-catalyst. The presence of a catalyst such as Sen-based catalyst, slurry method, bulk, solution, or are prepared by various polymerization methods such as continuous or batchwise by a gas phase method. Among them, in the present invention, those polymerized with a metallocene catalyst are preferable.
[0018]
Hydrogen can be used as a molecular weight regulator in the polymerization. The polymerization conditions are usually at a polymerization temperature in the range of -78 to 160 ° C, preferably 0 to 150 ° C, and usually normal pressure to 9 MPa, preferably 0 to A polymerization pressure in the range from 0.5 to 5 MPa is employed.
[0019]
In addition, the crystalline propylene-based polymer in the present invention is a polymer capable of obtaining a film having excellent low-temperature heat-sealing properties, anti-blocking properties, and scratch properties, for example, JP-A-2001-354717. And so on.
[0020]
Further, as the vinyl monomer in the modified propylene polymer constituting the heat-sealing material for the easily-openable container of the present invention, for example, styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, Aromatic vinyl compounds such as 4-methylstyrene, dimethylstyrene, and chlorostyrene; vinyl esters such as vinyl acetate and vinyl propionate; and (meth) acrylic acid [herein, “(meth) acryl” means “acryl” "And / or" methacryl ". ], Methyl (meth) acrylate, ethyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) (Meth) acrylic acid or its esters such as acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, and glycidyl (meth) acrylate; maleic anhydride, dimethyl maleate, and other di (2-ethylhexyl) maleate Examples thereof include unsaturated carboxylic acids or esters thereof, unsaturated nitriles such as (meth) acrylonitrile, and unsaturated mono- or dihalides such as vinyl chloride and vinylidene chloride. Among them, aromatic vinyl compounds are preferable. , Styrene, 2-methylstyrene It is particularly preferred, especially, styrene is preferred. In the present invention, two or more of these vinyl monomers may be used in combination.
[0021]
In the present invention, the modified propylene-based polymer contains 30 to 95% by weight of the crystalline propylene-based polymer, preferably 40 to 70% by weight, particularly preferably 45 to 65% by weight, and the vinyl monomer 70 to 95% by weight. It is obtained by subjecting 5% by weight, preferably 60 to 30% by weight, particularly preferably 55 to 35% by weight, to graft reaction conditions. If the vinyl monomer is less than this range, it may be used as a heat sealing material. Since the sealing force is too strong, it becomes difficult to open the container as an easily-openable container. On the other hand, if it exceeds this range, the homogeneity is impaired and the container cannot be put to practical use.
[0022]
In the present invention, as the graft reaction conditions, basically, conventionally known methods such as electron beam irradiation or addition of a radical generator under melt-kneading, under solution, under aqueous suspension or the like can be adopted. In the present invention, it is preferable to use an aqueous suspension method with the addition of a radical generator.
[0023]
For the aqueous suspension method with the addition of a radical generator, specifically, as the radical generator, those having a decomposition temperature of preferably 50 ° C. or higher, particularly preferably 50 to 130 ° C., and being oil-soluble are preferred. preferable. When the decomposition temperature is lower than 50 ° C., the polymerization of the vinyl monomer proceeds abnormally, and it tends to be difficult to obtain a homogeneous modified polymer. Here, the decomposition temperature is a temperature at which 50% of the radical generator is decomposed when 0.1 mol of the radical generator is added to 1 liter of benzene and left for 10 hours, so-called "10 hours". Half-life temperature ".
[0024]
In the present invention, examples of the radical generator include 2,4-dichlorobenzoyl peroxide (decomposition temperature 53 ° C.), t-butyl peroxypivalate (decomposition temperature 55 ° C.), and 3,5,5-trimethylhexa. Noyl peroxide (decomposition temperature 59.5 ° C), octanoyl peroxide (decomposition temperature 62 ° C), t-butylperoxy-2-ethylhexanoate (decomposition temperature 72.5 ° C), o-methylbenzoyl peroxide (Decomposition temperature 73 ° C), benzoyl peroxide (decomposition temperature 74 ° C), cyclohexanone peroxide (decomposition temperature 97 ° C), 2,5-dimethyl-2,5-di (benzoylperoxy) hexane (decomposition temperature 100 ° C) , T-butyl peroxybenzoate (decomposition temperature 104 ° C), di-t-butyl-diperoxy phthalate Organic peroxides such as methyl carbonate (decomposition temperature 107 ° C.), methyl ethyl ketone peroxide (decomposition temperature 109 ° C.), dicumyl peroxide (decomposition temperature 117 ° C.), di-t-butyl peroxide (decomposition temperature 124 ° C.), Examples include azo compounds such as azobis (2,4-dimethylvaleronitrile) (decomposition temperature 52 ° C.) and azobisisobutyronitrile (decomposition temperature 79 ° C.). In the present invention, two or more of these radical generators may be used in combination.
[0025]
The amount of the radical generator to be added is about 0.01 to 10 parts by weight based on 100 parts by weight of the vinyl monomer. If the amount is less than this range, the reaction does not proceed smoothly, and the amount is more than this range. And a gel tends to be easily generated in the modified polymer.
[0026]
Aqueous suspension graft reaction conditions suitable in the present invention include an aqueous suspension containing the crystalline propylene polymer, the vinyl monomer, and a predetermined amount of the radical generator, and decomposition of the radical generator. In this method, the vinyl monomer is impregnated with the crystalline propylene polymer by raising the temperature to a temperature that does not substantially occur, and then the temperature is further raised to complete the graft reaction.
[0027]
Here, the aqueous suspension is prepared by adding a vinyl monomer having a radical generator dissolved therein to an aqueous suspension of a crystalline propylene-based polymer and stirring the mixture or stirring the vinyl monomer having the radical generator dissolved therein. It is preferably prepared by any method of adding a crystalline propylene-based polymer to an aqueous suspension of a body and stirring the mixture.
[0028]
Further, the content of the crystalline propylene polymer and the vinyl monomer in the aqueous suspension is about 5 to 100 parts by weight with respect to 100 parts by weight of water, in order to maintain a stable dispersion state, For example, polyvinyl alcohol, methylcellulose, water-soluble polymers such as hydroxycellulose, anionic surfactants such as alkyl benzene sulfonate, nonionic surfactants such as polyoxyethylene alkyl ether, or magnesium oxide, calcium phosphate and the like It is preferable to use a suspension stabilizer such as a water-insoluble inorganic salt, alone or in combination, in an amount of about 0.01 to 10 parts by weight based on 100 parts by weight of water.
[0029]
The impregnation of the vinyl monomer into the crystalline propylene polymer is generally carried out at room temperature to 100 ° C., preferably 70 to 100 ° C., with stirring, and the free vinyl monomer is 20% of the total amount of the vinyl monomer. It is carried out to a level of not more than 5% by weight, preferably not more than 5% by weight, usually for about 2 to 8 hours. Since crystalline propylene-based polymers are relatively compatible with vinyl monomers, even if such vinyl monomers are liberated before the reaction starts, these vinyl monomers remain crystalline during the reaction. By impregnating the propylene-based polymer, a homogeneous modified polymer is obtained.
[0030]
The grafting reaction is generally performed under stirring at a temperature of about 50 to 150 ° C. and a pressure of about normal pressure to about 1 MPa for about 2 to 10 hours, and the temperature and pressure during that time need to be constant. There is no. The crystalline propylene-based polymer used in the reaction is used in the form of powder, and is preferably in the form of particles having an average particle size of 1 to 8 mm, particularly preferably 3 to 7 mm.
[0031]
In the present invention, as the modified propylene polymer, from the viewpoint of the sealing force as a heat sealing material and the ease of opening, the polymer of the vinyl monomer is contained in the matrix of the crystalline propylene polymer in an amount of 0%. It is preferable that the particles have a dispersed structure in which particles are dispersed with a particle diameter of 0.2 to 3 μm, and a crystalline propylene polymer in which the vinyl monomer is graft-polymerized is present at the interface.
[0032]
The heat-sealing material for an easily-openable container of the present invention containing the above-mentioned modified propylene-based polymer, the heat-sealing property at a low temperature, and for the purpose of improving the easy-opening property, etc. It may contain an olefin polymer other than the propylene polymer and / or a vinyl monomer polymer.
[0033]
Here, as the olefin-based polymer, for example, a homopolymer of an α-olefin having about 2 to 8 carbon atoms such as ethylene, propylene and 1-butene, and those α-olefins and ethylene, propylene, 1- Butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 4,4-dimethyl-1-pentene, 1-hexene, 4-methyl-1-hexene, 1-heptene, 1- Other alpha-olefins having about 2 to 18 carbon atoms, such as octene, 1-decene, and 1-octadecene, and copolymers with vinyl acetate, (meth) acrylic acid, (meth) acrylate, and the like are included. Specifically, for example, branched low-density polyethylene, ethylene homopolymer such as linear high-density polyethylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, Linear low, medium, etc., such as a tylene-propylene-1-butene copolymer, an ethylene-4-methyl-1-pentene copolymer, an ethylene-1-hexene copolymer, and an ethylene-1-octene copolymer. High-density ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene-based resin such as ethylene-ethyl (meth) acrylate copolymer, propylene Homopolymer, propylene resin such as propylene-ethylene copolymer, propylene-ethylene-1-butene copolymer, and 1-butene homopolymer, 1-butene-ethylene copolymer, 1-butene-propylene Examples thereof include 1-butene resins such as copolymers. Among them, branched low-density polyethylene is particularly preferred. In the present invention, two or more of these olefin polymers may be used in combination.
[0034]
Examples of the polymer of the vinyl monomer include polymers and copolymers of the same vinyl monomer as the vinyl monomer mentioned in the modified propylene-based polymer. Particularly preferred.
[0035]
In the present invention, the content of the olefin polymer and / or the polymer of the vinyl monomer contained in the modified propylene polymer is based on 100 parts by weight of the modified propylene polymer. Is preferably 800 parts by weight or less, more preferably 1 to 700 parts by weight, and particularly preferably 5 to 600 parts by weight.
[0036]
The heat for an easily-openable container of the present invention containing the modified propylene-based polymer, or the olefin-based polymer other than the modified propylene-based polymer, and / or the polymer of the vinyl monomer. In the sealing material, the graft and homopolymer of the vinyl monomer generated during the modification of the crystalline propylene-based polymer, and the total content of the polymer of the vinyl monomer further contained is 5%. It is preferably from 70 to 70% by weight, more preferably from 6 to 60% by weight, and particularly preferably from 7 to 50% by weight. If the total content of the vinyl monomer polymer is less than this range, the sealing force tends to be too strong as a heat sealing material to make opening difficult.On the other hand, if the content exceeds this range, the homogeneity is impaired and practical use is impaired. I can't get it.
[0037]
In addition, in addition to the modified propylene-based polymer, the olefin-based polymer and / or the vinyl monomer polymer, the heat-sealing material for an easily-openable container of the present invention has the effect of the present invention. To the extent not impaired, other thermoplastic resins and rubbers, and additives such as antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, antiblocking agents, lubricants, plasticizers, pigments, fillers, etc. May be blended. These compounds are added in advance to the crystalline propylene polymer to be modified, added to an olefin polymer or a vinyl monomer polymer, or added at the time of preparing a heat sealing material, During the production of the modified propylene-based polymer, for example, it may be added to a vinyl monomer together with a radical generator.
[0038]
The heat-sealing material for an easily-openable container according to the present invention comprises the modified propylene-based polymer, the olefin-based polymer or / and the polymer of the vinyl monomer used as needed, and other heat-resistant materials. After uniformly mixing a plastic resin, rubber, additives, etc. with a tumbler blender, ribbon blender, V-type blender, Henschel mixer, etc., melt kneading with a single or twin screw extruder, roll, Banbury mixer, kneader, Brabender, etc. It is prepared by
[0039]
The heat-sealing material for an easily-openable container of the present invention may be a single layer of the heat-sealing material, which may be used for a container lid or a container body as an easily-openable container. Resin, polyester resin, saponified ethylene-vinyl acetate copolymer, polycarbonate resin, polystyrene resin, acrylic resin, polyolefin resin and other thermoplastic resin films, aluminum foil, paper and other substrates As a laminating method, a conventionally known method such as a glue laminating method, an extruding laminating method, and a co-extrusion method with the above-mentioned various thermoplastic resins is employed. In this case, the thickness of the heat sealing material layer of the present invention is preferably about 5 to 100 μm.
[0040]
The easy-open container of the present invention has a heat-sealing structure in which the heat-sealing material for the easy-open container and the surface of the adherend are heat-sealed. The adherend is not particularly limited, but is preferably a propylene-based resin, and the propylene-based resin is the same as the olefin-based polymer other than the modified propylene-based polymer. A propylene-based resin may be used, and any single-layer or laminated state may be used as long as the propylene-based resin forms a surface.
[0041]
In the present invention, the specific form of the easy-open container, if the adherend is a propylene-based resin, for example, (1) as a packaging container comprising a container body and a lid, (a) the easy-open container of the present invention In the case where the heat-sealing material for a heat-resistant container is used on the lid material side, the heat-sealing material comprises a container body having a propylene-based resin on the heat sealing surface, and a lid material having the heat sealing material on the heat sealing surface. Easy-open container, (b) when the heat-sealing material for easy-open container of the present invention is used on the container body side, a container body having the heat-sealing material on the heat sealing surface, a propylene-based (2) As a packaging bag, (a) the case where the heat sealing material for an easily opening container of the present invention is used on both sides of a bag. An easy-open container that is a bag body heat-sealed with the heat-sealing material facing the heat-sealing materials of the bag member having the heat-sealing material on the heat-sealing surface, and (b) the easy-sealing container of the present invention. A case in which a heat sealing material for containers is used on one side of a bag, and a bag member having a propylene-based resin on the heat sealing surface is used on the other surface, and the heat sealing material is applied to the heat sealing surface. An easy-open container that is a bag body in which the bag member having the propylene-based resin and the propylene-based resin surface of the bag member having the propylene-based resin on the heat-sealing surface is heat-sealed.
[0042]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless departing from the gist of the present invention. The crystalline propylene polymers used in Examples and Comparative Examples are shown below.
[0043]
<Production Example of Crystalline Propylene Polymer (A)>
After sufficiently replacing the inside of a 1-liter stirred autoclave with propylene, introducing 230 ml of dehydrated and deoxygenated n-heptane and maintaining the temperature in the system at 40 ° C., JP-A-2001-354717 describes 10 g of montmorillonite chemically treated by the above method was added as a toluene slurry, and dimethylsilylenebis [1- {2-methyl-4- (4-chlorophenyl) -4H-azulenyl} synthesized and purified by the method described in the publication. A toluene solution of 0.15 mmol of racemic diloconium dichloride and 1.5 mmol of triisobutylaluminum is added, and then propylene is introduced at a rate of 10 g / hour for 120 minutes, and then polymerization is continued for 120 minutes. By removing the solvent under nitrogen and drying A solid catalyst component containing a Buropiren homopolymer .9g was prepared.
[0044]
On the other hand, after sufficiently replacing the inside of a 200-liter stirred autoclave with propylene, 45 kg of fully dehydrated liquefied propylene were introduced, and further, 500 ml (0.12 mmol) of a triisobutylaluminum n-heptane solution, 2.25 g of ethylene and 8.0 liters of hydrogen (as a standard volume) were added, and the temperature of the system was maintained at 30 ° C., and 1.2 g of the solid catalyst component prepared above was injected with argon to initiate polymerization. After raising the temperature to 65 ° C. over 30 minutes and maintaining the same temperature for 1 hour, the reaction was stopped by adding 100 ml of ethanol, the residual gas was purged, and the product was filtered and dried, whereby A crystalline propylene-ethylene copolymer (A) was produced.
[0045]
About the obtained crystalline propylene-ethylene copolymer (A), the melt flow rate was measured by the following method, the melt flow rate was 7.0 g / 10 minutes, the melting point [ _Tm ] was 125.0 ° C, and the weight average molecular weight [ The ratio [ _Mw / _Mn ] of the number [ _Mw ] to the number average molecular weight [ _Mn ] is 2.9, and the growth rate of the spherulite radius when the solidification temperature is [ _Tm- 30 ° C] and 95 ° C ( S) was 0.180 μm / sec.
[0046]
<Melt flow rate>
The measurement was performed at a temperature of 230 ° C. and a load of 21.18 N according to JIS K6921.
<Melting point>
Using a differential scanning calorimeter (manufactured by Seiko Instruments Inc.), 5.0 mg of a sample was held at 200 ° C. for 5 minutes in accordance with JIS 7121, and then cooled to 40 ° C. at a rate of 10 ° C./min for crystallization. Then, the melting point [T _m (° C.)] was defined as the top temperature of the melting peak observed when the sample was melted by heating at a rate of 10 ° C./min.
<Weight average molecular weight, number average molecular weight>
Using gel permeation chromatography ("GPC150C" manufactured by Waters), three columns ("AD80M / S" manufactured by Showa Denko KK), o-dichlorobenzene as a solvent, a concentration of 2 mg / 1 ml, and a temperature of 140 ° C, The polystyrene-equivalent weight average molecular weight [M _w ] and number average molecular weight [M _n ] were measured.
[0047]
<Growth rate of spherulite radius>
A polymer sample is sandwiched between two glass plates provided with a 20-μm-thick aluminum foil as a spacer, and heated on a hot plate at 200 ° C. for 5 minutes to form a sufficiently molten state. transferred to a "TC-600Ph"), under a nitrogen atmosphere, held for one minute at 200 ° C., then the temperature of the bath, as solidification temperature, the polymer melting point [T _m] from 30 ° C. lower temperature [T _m −30 ° C.], at a rate of 75 ° C./min, and observe the crystallization state at the same temperature ± 1 ° C. As an observation device, a CCD camera (“FDC-725” manufactured by Olympus Optical) was attached to a microscope (“BH-2” manufactured by Olympus Optical), and the obtained image data was used as freeware software provided by the National Institute of Health. The growth rate [S (μm / sec)] of the spherulite radius was determined from the slope of a straight line obtained by analyzing the NIM image and plotting the spherulite radius with respect to the elapsed time, and the average value of the 20 operations was obtained. .
[0048]
<Production example of crystalline propylene polymer (B)>
After sufficiently replacing the inside of the stirred autoclave having an internal volume of 200 liters with propylene, 60 liters of dehydrated and deoxygenated n-heptane were introduced, and further, 45 g of diethylaluminum chloride and titanium trichloride (manufactured by M & M Co., Ltd.). ) 16 g were introduced at 55 ° C under a propylene atmosphere and subsequently 5.8 kg / h propylene and 0.36 kg / h ethylene at 55 ° C, while maintaining the gas phase hydrogen concentration at 5.5% by volume. After introducing for 4 hours at a time rate and further continuing polymerization for 1 hour, a crystalline propylene-ethylene copolymer (B) was produced by purging the remaining gas, filtering and drying the product.
[0049]
The obtained crystalline propylene-ethylene copolymer (B) was measured in the same manner as described above, having a melt flow rate of 5.1 g / 10 min, a melting point [T _m ] of 135.0 ° C., and a weight average molecular weight. The ratio [ _Mw / _Mn ] of [ _Mw ] to the number average molecular weight [ _Mn ] is 4.1, and the growth rate of the spherulite radius when the solidification temperature is [ _Tm- 30 ° C] and 105 ° C. (S) was 0.125 μm / sec.
[0050]
Examples 1-3, Comparative Examples 1-3
In an autoclave having a capacity of 50 liters, 20 kg of water, 0.6 g of sodium dodecylbenzenesulfonate as a suspending agent, and 0.6 kg of tribasic calcium phosphate as a suspending aid were added to form an aqueous medium. 6 kg of particles of the crystalline propylene-ethylene copolymer (A) or (B) having an average particle diameter of 3 to 4 mm were added, and stirred to form an aqueous suspension. To this aqueous suspension, 6 kg of a styrene monomer in which 15.6 g of 3,5,5-trimethylhexanoyl peroxide and 9 g of benzoyl peroxide were dissolved as a radical generator were added, and nitrogen was introduced into the autoclave to allow the system to react. After pressurizing to 0.5 kg / cm ² , the inside of the autoclave was heated to 65 ° C., and stirred at this temperature for 6 hours to impregnate the propylene-based polymer particles with the entire amount of the styrene monomer including the radical generator. I let it. Subsequently, the inside of the autoclave was heated to 100 ° C., and the graft reaction was performed by stirring at this temperature for 3 hours. The temperature was further raised to 120 ° C., and stirring was performed at this temperature for 12 hours to complete the reaction. After cooling, the reaction solid was taken out and washed with water to obtain 12 kg of each particle of each modified propylene-ethylene copolymer (A ′) or (B ′). The resulting modified propylene-ethylene copolymers (A ′) and (B ′) each contained 50% by weight of polystyrene.
[0051]
The pellets of each of the modified propylene-ethylene copolymers (A ′) and (B ′) obtained above or low-density polyethylene are further added to 100 parts by weight of the modified propylene-ethylene copolymer. (Melt flow rate measured at a density of 0.913 g / cm ³ at 190 ° C. under a load of 21.18 N: 7 g / 10 min) or polystyrene (density 1.1 g / cm ³ , measured at 200 ° C. under a load of 49.03 N) When a melt flow rate of 6 g / 10 minutes is added in the amount shown in Table 1, they are fed to a single-screw extruder, melt-kneaded at 210 ° C., and pelletized to form a pellet having a diameter of 35 mm with a T die. It is supplied to a film forming machine (manufactured by Placo), melt-extruded at 230 ° C. and cooled to form a 30 μm-thick film. It was adhered to a 20 μm-thick polyethylene terephthalate film using an agent to prepare a two-layer laminated film.
[0052]
On the other hand, on the flange portion of a rectangular container body produced by thermoforming from a 200 μm-thick polypropylene resin sheet, the laminated film was used as a lid, and the modified propylene-ethylene copolymer layer was used as an adhesive surface, The container was heat-sealed under the following conditions to prepare an easily-openable container. The peel strength of each of the obtained containers was measured by the following method. The results are shown in Table 1.
[0053]
<Peel strength>
Using a hot plate type heat sealer, the lid material was thermocompression bonded to the container body flange at a temperature of 140 ° C., 160 ° C., or 180 ° C., a pressure of 1.96 × 10 ⁵ Pa, and a time of 0.5 second with a width of 5 mm. The bonded portion was sampled at a length of 15 mm, and peeled in a direction perpendicular to the length at a temperature of 23 ° C. at a tensile speed of 300 mm / min using an Instron tensile tester to obtain a 180 ° peel strength (g / 15 mm). It was measured.
[0054]
[Table 1]

[0055]
【The invention's effect】
According to the present invention, a heat-sealing material for an easily-openable container and a heat-sealing material that can form a heat-sealing portion that can be easily opened at the time of opening while having a sufficient sealing force even at a low-temperature heat sealing, and An easily openable container used can be provided.

Claims (8)

It is obtained by subjecting 30 to 95% by weight of a crystalline propylene polymer satisfying the following conditions (1), (2) and (3) and 70 to 5% by weight of a vinyl monomer to a graft reaction condition. A heat sealing material for an easily-openable container, comprising a modified propylene-based polymer.
(1) The melting point [T _m (° C.)] measured by a differential scanning calorimeter is 110 to 160 ° C.
(2) Weight average molecular weight The number average molecular weight of [M _w] ratio [M _n] [M _w / M _n] is from 2.5 to 4.0.
(3) The growth rate [S (μm / sec)] of the spherulite radius when the solidification temperature is [T _m −30 ° C.] has the relationship of the following formula (Ia).
0.140 <S (Ia) The heat sealing material for an easily-openable container according to claim 1, wherein the crystalline propylene-based polymer is a propylene-ethylene-based copolymer. The heat sealing material for an easily-openable container according to claim 1 or 2, wherein the vinyl monomer is an aromatic vinyl compound. The graft reaction conditions of the modified propylene polymer are raised to an temperature at which the aqueous suspension containing the crystalline propylene polymer, vinyl monomer, and radical generator does not substantially decompose the radical generator. The easy-open container according to any one of claims 1 to 3, wherein the vinyl monomer is impregnated into the crystalline propylene polymer by heating, and then the temperature is further raised to complete the graft reaction. Heat sealing material. The heat sealing material for an easily-openable container according to any one of claims 1 to 4, further comprising an olefin polymer other than the modified propylene polymer, and / or a vinyl monomer polymer. The heat sealing material for an easily-openable container according to claim 5, wherein the olefin polymer other than the modified propylene polymer is low-density polyethylene, and the polymer of the vinyl monomer is polystyrene. Vinyl monomer in a heat-sealing material for an easily-openable container containing a modified propylene polymer, or an olefin polymer other than the modified propylene polymer, and / or a polymer of a vinyl monomer; The heat-sealing material for an easily-openable container according to any one of claims 1 to 6, wherein the content of the monomeric polymer is 5 to 70% by weight. An easily-openable container having a heat-sealing structure in which the heat-sealing material for an easily-openable container according to any one of claims 1 to 7 and a propylene-based resin surface are heat-sealed.