JP6885312B2 - White adhesive composition and laminate - Google Patents

Description

The present invention relates to white adhesive compositions and laminates.

As a packaging material for foods, medical products, cosmetics, etc., a composite of plastic films such as polyethylene, polypropylene, vinyl chloride, polyester, and nylon laminated in multiple layers is used. As an adhesive using these plastic films, those composed of a polymer polyol and an organic isocyanate compound obtained by reacting an aromatic polyvalent carboxylic acid anhydride are known. At this time, the gravure ink in the printing process is printed in the order of ink-based color, indigo-based color, red-based color, and yellow-based color, and the color-developing property of these color inks and the concealing property of the contents to be packaged in the packaging material. In many cases, after printing with a black-based color, an indigo-based color, a red-based color, or a yellow-based color ink, the entire surface is printed with a single white ink color.

For example, Patent Document 1 discloses an adhesive composed of a white pigment, a polyol component, and a polyisocyanate component, which has both the characteristics of a white ink and the characteristics of an adhesive (summary).
Further, Patent Document 2 discloses an adhesive containing a white pigment, a modified polyester, and a blocked isocyanate (claims 3 and 5).
Further, Patent Document 3 discloses an adhesive having a polyester resin, a polyisocyanate compound, a fluorescent compound, and titanium oxide.

Japanese Unexamined Patent Publication No. 2003-64342 Japanese Unexamined Patent Publication No. 2011-187602 Japanese Unexamined Patent Publication No. 2013-237735

Compared to the plain part, the white ink part of the laminated body for packaging materials may have lower adhesive strength due to cohesive failure of the ink layer after heat sterilization treatment such as boiling or retort, and has high hiding power. If necessary, white ink is overprinted, so that there is a problem that the adhesive strength is further lowered.

It is described that the adhesive composition disclosed in Patent Document 1 can amplify high adhesiveness in the white ink portion and high hiding property in the white ink portion. However, since the adhesive composition disclosed in Patent Document 1 has insufficient dispersibility, it is not possible to prevent the sedimentation of titanium oxide, and a good appearance can be obtained by high-speed coating at 100 m / min or more. could not.

The adhesive composition disclosed in Patent Document 2 is for attaching a plastic film to the can body of a metal can, and is laminated at 100 to 230 ° C. and then heated at a high temperature of 150 to 250 ° C. It seems that the adhesive is cured ([0003] to [0005]) to ensure adhesion. The adhesive disclosed in Patent Document 3 is also for metal cans as in the case of Patent Document 2, and is laminated at 120 to 200 ° C. and then baked at a high temperature of 180 to 230 ° C. ([0052]. ]), It seems that the adhesiveness is secured.
However, when bonding plastic films that are easily damaged by heat, or a much thinner metal foil instead of a plate and a plastic film that is easily damaged by heat, the adhesive must be cured at a high temperature as described above. Therefore, the adhesive compositions disclosed in Patent Documents 2 and 3 cannot exhibit sufficient adhesive strength by low-temperature curing.
Further, Patent Document 2 describes that laminating is performed at an extremely low speed of 1 m / min. The adhesive composition disclosed in Patent Document 2 has insufficient dispersibility and cannot prevent sedimentation of titanium oxide. In addition, agglomerated titanium oxide roughens the coated surface during high-speed coating, so that the appearance of the adhesive composition is large. Defects are likely to occur. Patent Document 3 discloses a laminating speed of 50 m / min, but does not suggest any coating or laminating at a high speed of 100 m / min or more. The adhesive compositions disclosed in Patent Documents 2 and 3 could not obtain a good appearance by coating or laminating at a high speed of 100 m / min or more.

An object of the present invention is to provide a white adhesive composition which has excellent sedimentation stability and can form a laminated body having a good appearance even when coated and laminated at high speed and having excellent whiteness.

The present invention relates to a white adhesive composition containing all of the conditions (1) to (4) containing a polyester polyol (A), a polyisocyanate component (B), and a white pigment (C).
An adhesive composition containing a polyester polyol (A), a polyisocyanate component (B), and a white pigment (C), which satisfies all of the following conditions (1) to (4).
(1) The polyester polyol (A) has an acid value of 0.8 mg / KOH or more and 15 mg / KOH or less, a glass transition temperature of −10 ° C. to 10 ° C., and a number average molecular weight of 4000 to 50000.
(2) The content of the aromatic monomer is higher than 35% by mass in the total of 100% by mass of the acid component (a1) and the alcohol component (a2) which are the constituent monomers of the polyester polyol (A). There are many.
(3) The polyisocyanate component (B) is contained in an amount of 10 to 60 parts by mass with respect to 100 parts by mass of the polyester polyol (A).
(4) When the total of the polyester polyol (A), the polyisocyanate component (B), and the white pigment (C) is 100% by mass, the content of the white pigment (C) is 10 to 34% by mass. is there.

The acid component (a1), which is a constituent monomer of the polyester polyol (A), preferably contains two or more kinds of aromatic polybasic acids.

The present invention also relates to a packaging laminate obtained by laminating a plastic film that can be softened at 200 ° C. or lower and another sheet-like base material using the white adhesive composition of the present invention.

INDUSTRIAL APPLICABILITY According to the present invention, it is provided to provide a white adhesive composition which has excellent sedimentation stability and can form a laminate having a good appearance even when coated and laminated at high speed and having an excellent whiteness. Can be done.

As described above, the adhesive composition of the present invention contains a polyester polyol (A), a polyisocyanate component (B), and a white pigment (C).

<Polyester polyol (A)>
From the viewpoint of dispersibility, it is important that the polyol used in the present invention has an acid value of 0.8 to 15 (mg / KOH), preferably 1 to 5. Further, from the viewpoint of adhesive strength, it is important that the glass transition temperature is −10 ° C. to 10 ° C., preferably −5 ° C. to 10 ° C. Further, from the viewpoint of the viscosity of the adhesive composition, it is important that the number average molecular weight is 4,000 to 50,000, preferably 4,000 to 20,000. Further, the content of the aromatic monomer is more than 35% by mass in the total of 100% by mass of the acid component (a1) and the alcohol component (a2) which are the constituent monomers of the polyester polyol (A). is important.
Further, a polyether ester polyol, a polyester amide polyol, a polyester polyurethane polyol, castor oil or a mixture thereof (hereinafter, these are referred to as polyol (1)) and the like can be copolymerized and blended.

Examples of the polyester polyol include dibasic acids such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, and sebatic acid, dialkyl esters thereof, or mixtures thereof, and examples thereof include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, and neo. Glycos such as pentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 3,3'-dimethylol heptane, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol or Polyester polyols obtained by polymerizing oxylane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using a low-volume polyol such as water, ethylene glycol, propylene glycol, trimethylolpropane, and glycerin as an initiator. Examples thereof include polyester polyols obtained by reacting with a mixture, and polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, and poly (β-methyl-γ-valerolactone). Further, in the esterification reaction, for example, a polyester amide polyol obtained by using an aliphatic diamine having an amino group such as ethylenediamine, propylenediamine and hexamethylenediamine as a raw material can also be used.

Further, from the viewpoint of heat resistance, a polyester polyurethane polyol can also be used. The polyester polyurethane polyol is a polyol having a urethane bond in one molecule. For example, a polyester polyol having a number average molecular weight of 200 to 20,000, a polyether ester polyol, or the like and a polyisocyanate in a state where the NCO / OH is less than 1. It is preferably obtained by reacting with, and more preferably obtained by reacting with 0.9 or less.

In the present invention, as the above-mentioned polyol, one having a carboxyl group in the molecule (inside the molecule or at the end of the molecule) (hereinafter referred to as polyol (2)) can be used. The polyol (2) used in the present invention is preferably obtained by reacting the above-mentioned polyol (1) with a polybasic acid or an anhydride thereof. The polyol (1) used at this time may contain two or more hydroxyl groups at the molecular ends and have a number average molecular weight of 4,000 to 50,000 from the viewpoint of dispersion stability and high-speed coating appearance. It is important, preferably 4,000 to 20,000. When the number average molecular weight is 4,000 or more, the dispersion stability is sufficient, and when it is 100,000 or less, a good appearance can be obtained at the time of coating.

<Isocyanate compound (B)>
Examples of the isocyanate used in the present invention include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, and 1,3-butylene diisocyanate. , 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl caproate and other aliphatic diisocyanates;
1,4-Cyclohexanediisocyanate, 1,3-Cyclohexanediisocyanate, 3-Isocyanatemethyl-3,5,5-trimethylcyclohexylisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), methyl2,4-cyclohexanediisocyanate, methyl2 , 6-Cyclohexanediisocyanate, 1,4-bis (isocyanatemethyl) cyclohexane, 1,3-bis (isocyanatemethyl) cyclohexane and other alicyclic diisocyanates;
m-phenylenediisocyanate, p-phenylenediocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-2,6-tolylene diisocyanate or 2,6-tri Aromatic diisocyanates such as range isocyanates or mixtures thereof, 4,4'-toluene diisocyanates, dianisidine diisocyanates, 4,4'-diphenyl ether diisocyanates;
1,3-1,4-xylylene diisocyanate or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω'-diisocyanate-1,4-diethylbenzene, 1,3-bis (1-isocyanate-1-methylethyl) ) Aromatic diisocyanates such as benzene or 1,4-bis (1-isocyanate-1-methylethyl) benzene or a mixture thereof;
Triphenylmethane-4,4', 4 "-
Organic triisocyanates such as triisocyanate, 1,3,5-triisocyanatebenzene, 2,4,6-triisocyanate toluene; 4,4'-diphenyldimethylmethane-2,2'-5,5'-tetraisocyanate and the like. Polyisocyanate monomer such as organic tetraisocyanate;
Dimers, trimmers, biurets, allophanates derived from the above polyisocyanate monomers;
Polyisocyanate having a 2,4,6-oxadiazine trione ring obtained from carbon dioxide gas and the above polyisocyanate monomer; ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, 1,6- Hexandiol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolpropane, cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerol, An adduct of a low molecular weight polyol having a molecular weight of less than 200, such as trimethylolpropane, pentaerythritol, and sorbitol, and the polyisocyanate monomer;
Polyester polyol, polyether ester polyol, polyesteramide polyol, polycaprolactone polyol, polyvalerolactone polyol, acrylic polyol, polycarbonate polyol, polyhydroxyalkane, castor oil, polyurethane polyol, etc. having a molecular weight of 200 to 20,000 and the above polyisocyanate monomer Additive with
Examples thereof include an adduct of a polyurethane polyol obtained by reacting a polyether polyol and a polyisocyanate with an NCO / OH of less than 1 and the polyisocyanate monomer.
These polyisocyanate compounds can be appropriately used alone or as a mixture of two or more kinds depending on the use of the adhesive. For example, from the viewpoint of curing speed and heat resistance, aromatic polyisocyanates are preferable.
From the viewpoint of curing rate, the isocyanate compound (B) is preferably contained in an amount of 1 to 60 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of the polyol (A).

<White pigment (C)>
It is important that the adhesive of the present invention contains a white pigment (C) in order to impart hiding power. As the white pigment, titanium oxide, calcium carbonate, precipitating barium sulfate, talc, clay and the like are used, but titanium oxide is preferable in terms of whiteness and concealment.
Among the titanium oxides, it is preferable to include the rutile type. Examples of titanium oxide containing rutile type include Tipaqre CR-50, R-630, R-550, R-820, R-930, CR-80, R-830, CR-97, CR-90, CR-93. , CR-95, CR-58, CR-67, R-580, R-670 (manufactured by Ishihara Sangyo Co., Ltd.), Titanium JR-407, JR-600A, JR-600E, JRNC, JR-602, JR-603 , JR-701, JR-603, JR-805, JR-808, JR-300 (manufactured by Teika Co., Ltd.), Titanium R-650, R-5N, R-61N, R-52N, R-62N, SR- 1, R-GL, TCR-37, TCR-10, TCR-17, TCR-61, TCR-57, TCR-11 (manufactured by Sakai Chemical Co., Ltd.), Kronos KR-380, KR-380N, KR-310 ( Titanium Industry Co., Ltd., FR-22, FR-41, FR-35, FR-44, FR-46 (Furukawa Machinery Metals Co., Ltd.), TR-700, TR-840 (Fuji Titanium Co., Ltd.) , Ti-PureR-900, R-920, R-902, R-960, R-901 (manufactured by DuPont Group), TioxideR-HD2, R-HD6, R-TC4, R-HD3, R-TC90, R-CR2, R-CR3, R-CR6, R-TC60, R-TCY, R-CR60, R-TC90 (manufactured by Tioxide Group) can be mentioned.

The white adhesive of the present invention is a mixture of polyester polyol (A) and white pigment (C), and known dispersers such as Eiger mill, paint shaker, paint conditioner, scandex, sand mill, ball mill, colloid mill, etc. It can be obtained by dispersing the isocyanate compound (B) using a stirrer such as a dysper or a homomixer, and then mixing the isocyanate compound (B). Further, various additives can be added to the dispersion liquid of the polyester polyol (A) and the white pigment (C), or can be added after mixing the isocyanate compound (B).

<Silane coupling agent>
The adhesive of the present invention may further contain a silane coupling agent in order to increase heat resistance and water resistance. Examples of the silane coupling agent include trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane, 3-aminopropyltriethoxysilane, and N- (2-aminoethyl) 3-aminopropyltrimethoxysilane. It has a glycidyl group such as trialkoxysilane having an amino group such as 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane. Examples thereof include trialkoxysilane. The amount of the silane coupling agent added is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the polyester polyol (A).

<Phosphorus oxygen acid>
In addition, the adhesive of the present invention may further contain an oxygen acid of phosphorus or a derivative thereof in order to enhance acid resistance. Among the oxygen acids of phosphorus or derivatives thereof, the oxygen acid of phosphorus may be any one having at least one free oxygen acid, for example, hypophosphoric acid, phosphoric acid, orthophosphoric acid, the following. Examples thereof include phosphoric acids such as phosphoric acid, and condensed phosphoric acids such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, and ultraphosphoric acid. Examples of the derivative of the oxygen acid of phosphorus include those in which the oxygen acid of phosphorus is partially esterified with alcohols while leaving at least one free oxygen acid. Examples of these alcohols include fatty alcohols such as methanol, ethanol, ethylene glycol and glycerin, and aromatic alcohols such as phenol, xylenol, hydroquinone, catechol and fluoroglycinol. The oxygen acid of phosphorus or a derivative thereof may be used in combination of two or more.
The amount of phosphorus oxygen acid or a derivative thereof added is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, based on the solid content of the adhesive, and is 0.1. It is particularly preferably ~ 1% by weight.

<Epoxy phosphate>
Further, the adhesive of the present invention can contain an epoxy phosphate in order to improve the adhesion performance to a metal. Examples of the phosphoric acid epoxy include URAD-DD79 manufactured by DSM Resins Resin Co., Ltd.
The amount of the phosphoric acid epoxy added is preferably 0.01 to 10% by weight, particularly preferably 0.1 to 1% by weight, based on the solid content of the adhesive.

<Other additives>
The adhesive of the present invention further contains, for example, additives such as an antioxidant, an ultraviolet absorber, an antioxidant, a fungicide, a thickener, a plasticizer, a pigment, and a filler, if necessary. Can be made to. In addition, known catalysts, additives and the like can be contained in order to control the curing reaction.
The adhesive of the present invention contains a polyester polyol (A), a polyisocyanate component (B), and a white pigment (C), and has a viscosity of 100 to 10,000 mPa at room temperature to 150 ° C., preferably room temperature to 100 ° C. -S, preferably 100 to 5,000 mPa · s, can also be used as a solvent-free type. If the viscosity of the adhesive is higher than the above range, it may be diluted with an organic solvent. As the organic solvent, for example, any solvent may be used as long as it is inactive against isocyanates such as ester-based solvents such as ethyl acetate, ketone-based solvents such as methyl ethyl ketone, and aromatic hydrocarbon-based solvents such as toluene and xylene. You may.

The adhesive of the present invention is applied to the film surface with a solvent-type or solvent-free laminator, and in the case of the solvent type, the solvent is volatilized, and in the case of the solvent-free type, the adhesive surface is directly bonded and heated at room temperature or under heating. It can be used by curing it. Generally, it is convenient to use the solvent-free type in the range of the dry solid amount of 1.0 to 2.0 g / m ² and the solvent type in the dry solid amount of 2.0 to 5.0 g / m ^2.

<Laminated body>
Next, the laminated body of the present invention will be described. The laminate of the present invention is one in which at least two sheet-like substrates are laminated via an adhesive layer formed from the adhesive of the present invention.
The sheet-like base material is a plastic film, paper, metal foil or the like usually used for a laminate, and the two sheet-like base materials may be of the same type or different types. As the plastic film, a film made of a thermoplastic resin or a thermosetting resin can be used, but a film made of a thermoplastic resin is preferable.
The thermoplastic resin is preferably one that can be softened at a temperature of 200 ° C. or lower, and is preferably a polyolefin, polyester, polyamide, polystyrene, vinyl chloride resin, vinyl acetate resin, ABS resin, acrylic resin, acetal resin, polycarbonate resin, or fibrous resin. Examples include plastic.

The thickness of the laminate is usually 10 μm or more. To make a laminate using the adhesive of the present invention, the adhesive is applied to one side of one sheet-like substrate by a commonly used method, for example, a dry laminator, and the solvent is volatilized, and then the solvent is volatilized. It may be bonded to the other sheet-like substrate and cured at room temperature or under heating. The amount of adhesive applied to the surface of the sheet-like substrate is about ^{1 to 10 g / m 2.}

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Parts and% in Examples and Comparative Examples mean parts by weight and% by weight unless otherwise specified.
Further, in the present invention, the "number average molecular weight" was calculated using a calibration curve of standard polystyrene using gel permeation chromatography. The acid value and hydroxyl value are expressed in mg of KOH per 1 g of polymer polyol. The acid value was measured by neutralization titration with KOH, and the hydroxyl value was measured by acetylation using pyridine and acetic anhydride.
The "aromatic monomer content" is the mass of a monomer having an aromatic ring used when performing a dehydration reaction in esterification excluding urethanization and acid denaturation by the following formula. Is.
Aromatic monomer content = mass of aromatic monomer ÷ (mass of all carboxylic acid components + mass of all hydroxyl groups) x 100

(Synthesis Example 1) Synthesis of polyester polyol (a-1) solution In a reaction vessel equipped with a stirrer, a thermometer, a reflux cooling tube, a dropping tank and a nitrogen gas introduction tube, 148 parts of terephthalic acid and 222 parts of isophthalic acid are used as acid components. , 226 parts of adipic acid, 51 parts of 1,6-hexanediol, 84 parts of ethylene glycol, 219 parts of 2-methyl-1,3-propanediol and 7 parts of trimethylolpropane as alcohol components, and stirred under a nitrogen stream. While doing so, the temperature was raised to 260 ° C. After continuing the reaction until the acid value became 5 or less, the pressure was gradually reduced to continue the reaction at 1 mmHg, excess alcohol was removed, 4.8 g of trimellitic anhydride was added, and 1 at 180 ° C. After holding for a long time, a polyester polyol (a-1) having an acid value of 1.89 mgKOH / g, a number average molecular weight of 11000, Tg-5 ° C., and an aromatic monomer content of 38.7% was obtained and diluted with ethyl acetate. A solution having a solid content of 50% was obtained.

(Synthesis Examples 2, 5, 6-7, 10-11)
According to the composition shown in Table 1, a solution of each polyester polyol was obtained in the same manner as in Synthesis Example 1.

(Synthesis Example 3) Synthesis of polyester polyurethane polyol (a-3) solution In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas introduction tube, 371 parts of isophthalic acid and 226 adipic acid are used as acid components. 51 parts of 1,6-hexanediol, 84 parts of ethylene glycol, 219 parts of 2-methyl-1,3-propanediol and 7 parts of trimethylolpropane were charged as alcohol components, and the temperature was 260 ° C. while stirring under a nitrogen stream. The temperature was raised to. After continuing the reaction until the acid value became 5 or less, the pressure was gradually reduced to continue the reaction at 1 mmHg to remove excess alcohol, and then 14 g of isophorone diisocyanate was added in an atmosphere of 150 ° C. and stirred. Continued. After continuing stirring until the absorption derived from unreacted NCO disappeared by IR analysis, 2.4 g of trimellitic anhydride was added and kept at 180 ° C. for 1 hour, and the acid value was 1.0 mgKOH / g, number. A polyester polyol (a-3) having an average molecular weight of 42000, Tg of 0 ° C. and an aromatic monomer content of 38.9% was obtained and diluted with ethyl acetate to obtain a solution having a solid content of 50%.

(Synthesis Examples 4, 8-9)
According to the composition shown in Table 1, a solution of each polyester polyurethane polyol was obtained in the same manner as in Synthesis Example 3.

The symbols in Table 1 are as follows.
TMA: Trimellitic anhydride 1,6-HD: 1,6-Hexanediol EG: Ethylene glycol NPG: Neopentyl glycol MPO: 2-Methyl-1,3-propanediol DEG: Diethylene glycol TMP: Trimethylolpropane IPDI: Isophorone Diisocyanate

(Mixing of white pigment)
(Formulation Example 1 for Examples) Formulation of white polyol (A-1) 146 parts of a solution of polyester polyol (a-1) having a solid content of 50% (including 73 parts of polyester polyol (a-1)), oxidation 27 parts of titanium (JR-407, manufactured by Teika Co., Ltd.) and 27 parts of ethyl acetate solvent were mixed by stirring and kneaded with a sand mill to obtain a white polyol composition (A-1) having a solid content of 50%, which will be described later. The sedimentation stability was evaluated according to the method used. The results are evaluated and the results are shown in Table 2.

(Formulation Examples 2 to 10 for Examples), (Formulation Examples 11 to 16 for Comparative Examples)
According to Table 2, white polyol compositions (A-2) to (A-16) were obtained in the same layers as in Formulation Example 1, and the sedimentation stability was evaluated according to the method described later. The results are evaluated and the results are shown in Table 2.

(Settlement stability test)
The white polyol compositions (A-1) to (A-16) were placed in a glass bottle with a lid and stored at a temperature of 40 ° C. for 1 month. The appearance after storage was evaluated according to the following criteria.
◯: No separation between the solution and the pigment was observed, and there was no sedimentation on the bottom surface.
Δ: No separation between the solution and the pigment was observed, and there was sedimentation on the bottom surface.
X: Separation of solution and pigment is observed.

As shown in Table 2, it can be seen that the white pigment-containing polyester polyol composition using the specific polyester polyol specified in the present invention is excellent in sedimentation stability after one month at 40 ° C. On the other hand, when a polyester polyol (a-6) having a low acid value was used or a polyester polyol (a-9) having a low molecular weight was used, the dispersed state of the white pigment could not be kept stable. Therefore, no adhesive was produced and no laminate was formed.

(Example 1)
Composition 200 of white polyol (A-1) having a solid content of 50% obtained in Formulation Example 1 for Examples in a reaction vessel provided with a stirrer, a thermometer, a reflux cooling tube, a dropping tank and a nitrogen gas introduction tube. As the polyisocyanate component (B), 14 parts of ethyl acetate diluted solution (nonvolatile content 75% by weight) of trimethylolpropane adduct (TDI-TMP adduct) of tolylene diisocyanate and 62.3 parts of ethyl acetate were blended. An adhesive having a solid content of 40% was obtained, and the adhesive strength, coating appearance, heat resistance, and whiteness were evaluated according to the method described later. The results were evaluated and the results are shown in Table 3.

(Examples 2 to 6, Comparative Examples 1 to 8)
An adhesive was obtained by the same operation as in Example 1 except that the materials shown in Table 3 were used, evaluated in the same manner, and the results are shown in Table 3.

(Creation of 4-layer laminate)
The adhesive was first applied to the printed surface of a polyethylene terephthalate (PET) film with a thickness of 12 μm using a laminator at room temperature at a coating speed of 200 m / min and a solid content coating amount of 3.0 g / m ² to volatilize the solvent. After that, the coated surface was bonded to the corona discharge-treated surface of an unstretched polyethylene (PE) film having a thickness of 50 μm, and kept warm at 40 ° C. for 2 days to prepare a 4-layer laminate.

(Adhesive strength-initial)
A test piece having a size of 15 mm × 300 mm was prepared from the four-layer laminate prepared as described above, and the peeling speed was obtained by T-type peeling under the conditions of a temperature of 20 ° C. and a relative humidity of 65% using a tensile tester. The adhesive strength (N / 15 mm) between the PET film and the PE film was measured at 30 cm / min. This test was performed 5 times, and the average value was calculated and evaluated according to the following criteria.
⊚: Adhesive strength 8N or more ○: Adhesive strength less than 8N, 5N or more Δ: Adhesive strength less than 5N, 3N or more ×: Adhesive strength less than 3N

(Adhesive strength-after heat resistance test)
"RCS-40RTGN" manufactured by Hisaka Seisakusho Co., Ltd. High-temperature and high-pressure cooking sterilization tester, 10r. p. m. After hot water sterilization was performed on each laminate under pressure of 135 ° C. for 30 minutes and 3 MPa, the adhesive strength was measured in the same manner as in the adhesive strength test. This test was performed 5 times, the average value was calculated, and the evaluation was made according to the same criteria.

(Appearance of the laminate)
The laminate was visually observed from the PET side and evaluated according to the following criteria.

⊚: No yuzu-skin-like pattern or small spot-like pattern is observed on the laminate.
◯: No small spot-like pattern is observed on the laminate, but some yuzu-skin-like pattern is observed. A level that does not cause any problems in use.
Δ: No small spot-like pattern is observed in the vapor-deposited portion, but many yuzu-skin-like patterns are observed. A level that does not cause any problems in use.
X: Not only yuzu-skin-like patterns but also many small spot-like patterns are observed on the laminate.

(Confirmation of white density)
The hiding power of the laminate from the PE side was evaluated by whiteness using ^{L *} measured using a color difference meter (X-Rite eXact manufactured by Japanese corporation X-Rite). That is, the higher this value, the higher the whiteness and the better the concealing property. Each measurement was an average value of 5 points and evaluated according to the following criteria.
◯: L ^* is 70 or more.
Δ: L ^* is less than 70 and 60 or more.
X: L ^* is less than 60.

The symbols in Table 3 are as follows.
HDI-Buret: Hexamethylene diisocyanate burette IPDI-TMP: Isophorone diisocyanate trimethylolpropane adduct XDI-TMP: Xylylene diisocyanate trimethylolpropane adduct IPDI-TMP / XDI-TMP: IPDI-TMP and XDI -A mixture of 6: 4 (mass ratio) with TMP.

As shown in Table 3, it can be seen that the laminates using the adhesive of the present invention of Examples 1 to 6 are excellent in various performances.
On the other hand, in Comparative Example 1, a high acid value polyester polyol (a-7) was used, and in Comparative Example 2, a high molecular weight polyester polyol (a-8) was used, so that the viscosity of the adhesive increased. Therefore, the coating appearance of the laminated body is inferior. In Comparative Example 3, since a polyester polyol (a-10) having a small aromatic circulation was used, the adhesive strength of the laminate at the initial stage and after the heat resistance test was inferior. In Comparative Example 4, since the polyester polyol (a-11) having a high glass transition temperature was used, the initial adhesive strength of the laminated body was inferior. Adhesive strength is inferior.
In Comparative Example 5, the white density is inferior because the amount of titanium oxide compounded is small. In Comparative Example 6, since the amount of titanium oxide compounded is too large, the initial adhesive strength of the laminated body is inferior. In Comparative Example 7, since the amount of the polyisocyanate component blended is too small, the adhesive strength at the initial stage of the laminate and after the heat resistance test is inferior. In Comparative Example 8, since the amount of polyisocyanate compounded is too large, the initial adhesive strength of the laminate is inferior.

Claims (3)

A white adhesive composition containing a polyester polyol (A), a polyisocyanate component (B), and a white pigment (C), which satisfies all of the following conditions (1) to (4). ..
(1) The polyester polyol (A) has an acid value of 0.8 to 15 (mg / KOH), a glass transition temperature of −10 ° C. to 10 ° C., and a number average molecular weight of 4000 to 50000.
(2) The content of the aromatic monomer is higher than 35% by mass in the total of 100% by mass of the acid component (a1) and the alcohol component (a2) which are the constituent monomers of the polyester polyol (A). There are many.
(3) When the total of the polyester polyol (A), the polyisocyanate component (B), and the white pigment (C) is 100% by mass, the polyisocyanate component (B) is contained in an amount of 10 to 60% by mass.
(4) When the total of the polyester polyol (A), the polyisocyanate component (B), and the white pigment (C) is 100% by mass, the content of the white pigment (C) is 10 to 34% by mass. is there. The white adhesive composition according to claim 1, wherein the acid component (a1) which is a constituent monomer of the polyester polyol (A) contains two or more kinds of aromatic polybasic acids. A packaging laminate obtained by laminating a plastic film that can be softened at 200 ° C. or lower and another sheet-like base material using the white adhesive composition according to claim 1 or 2.