JPS6210553B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to water-soluble or water-dispersible hot melt adhesives, and more particularly to water-soluble or water-dispersible hot melt adhesives suitable for bookbinding packaging, paper tubes, heat-sensitive and rewetting tapes, labels or adhesive interlining. It relates to hot melt adhesives. Hot melt adhesives have the advantages of low toxicity and low pollution because they do not use solvents, and are easy to work with because they do not require a drying process. Used as an adhesive. Polyvinyl alcohol (hereinafter abbreviated as PVA) is a typical adhesive used in an aqueous solution, but requires a solution preparation process and a drying process after adhesion. Moreover, PVA has a strong intermolecular bonding force of hydroxyl groups in its molecular structure, and its melting point and decomposition point are close to each other, making it difficult to melt.
PVA cannot be used as a hot melt adhesive. In recent years, there has been a desire to save resources and collect and reuse waste paper, but the hot melt adhesives currently in use are mainly made of ethylene-vinyl acetate copolymer and are insoluble in water. During the recycling process, there were problems such as resin remaining in the waste paper adhering to the paper roll, causing problems such as paper breaks and pinholes. In order to solve these problems, it is desired to develop a water-soluble hot melt adhesive. In order to meet such demands, the present inventors previously proposed a water-soluble and heat-melting adhesive that uses polyvinyl alcohol with a low degree of polymerization and saponification as a base polymer (Japanese Patent Laid-Open No. 51-96832). . However, since this adhesive has a high softening point, it is necessary to use it at a high temperature, and because it is not sufficiently compatible with plasticizers, it tends to soften at high temperatures and high humidity, making it difficult to use. The present inventors continued their research to lower the softening point of the above adhesive, and as a result, by copolymerizing allyl acetate, a rewetting hot melt adhesive with a lower softening point and improved rewetting properties was obtained. We discovered this and made a separate proposal (Japanese Patent Application Laid-Open No. 102937/1983). Although this adhesive had a lower softening point and improved thermal meltability, it became more likely to soften at high temperatures and high humidity, and its blocking properties were somewhat poor. As a result of continued research by the present inventors to improve the heat resistance, moisture resistance, and compatibility of the adhesive,
It was discovered that a partially saponified copolymer obtained by copolymerizing vinyl acetate and vinyl saturated branched fatty acids has increased strength at high temperatures and high humidity, as well as improved compatibility, and separately proposed it (Patent Application No. 1983-3556). However, in this case, the meltability was only slightly improved. As a result of continued research to obtain an ideal adhesive as a water-soluble hot melt adhesive, the present inventors discovered a copolymer obtained by copolymerizing a specific saturated branched fatty acid vinyl, allyl acetate, and vinyl acetate in a specific ratio. The present invention was achieved by discovering that the above object can be achieved by partially saponifying the coalescence. That is, the present invention provides (a) general formula CH ₂ =
CHOCOCR ₁ R ₂ R ₃ (R ₁ R ₂ R ₃ represents an alkyl group.) Saturated branched fatty acid vinyl 0.5
Intrinsic viscosity obtained by copolymerizing ~10 parts by weight of allyl acetate, 1 to 40 parts by weight of allyl acetate, and 100 parts by weight of vinyl acetate (measured in acetone solvent at 30°C, concentration unit: g/100ml).
This is a water-soluble or water-dispersible hot melt adhesive made of a partially saponified product of a 0.09 to 0.35 copolymer by saponifying 50 to 85 mol% of the vinyl acetate portion and allyl acetate portion to form hydroxyl groups. The hot melt adhesive of the present invention has excellent heat resistance and moisture resistance, and has good compatibility with thermoplastic resins and plasticizers that are well known as additive components of hot melt adhesives. It also has excellent melting properties. The saturated branched fatty acid vinyl used in the preparation of the hot melt adhesive of the present invention has the general formula CH ₂ =
CHOCOCR ₁ R ₂ R ₃ (R ₁ R ₂ R ₃ is an alkyl group)
This is shown in . The sum of the carbon numbers of the alkyl groups of R ₁ R ₂ and R ₃ is preferably 3 to 12, especially 6 to 12, considering the water solubility of the partially saponified product obtained and the compatibility with the thermoplastic resin and plasticizer. desirable. The hot melt adhesive of the present invention is prepared by polymerizing such saturated branched fatty acid vinyl, allyl acetate and vinyl acetate in a specific ratio to obtain a copolymer, and partially saponifying the obtained copolymer. During copolymerization, 0.5 to 10 parts by weight of saturated branched fatty acid vinyl, preferably 2 to 6 parts by weight, and 1 to 40 parts by weight of allyl acetate per 100 parts by weight of vinyl acetate.
It is necessary to use preferably in a proportion of 5 to 20 parts by weight. The amount of saturated branched fatty acid vinyl used is
If it is less than 0.5 parts by weight, the copolymerization effect will be reduced, while if it exceeds 10 parts by weight, the water solubility of the partially saponified product obtained will be extremely reduced, which is not suitable.
Furthermore, if the amount of allyl acetate used is less than 1 part by weight, the effect of lowering the softening point due to copolymerization will be reduced,
On the other hand, if it exceeds 40 parts by weight, radical copolymerization tends to become difficult due to the chain transfer and polymerization retardation effects of allyl acetate, and furthermore, the blocking properties of the partially saponified product obtained deteriorate, which is not suitable. The polymerization may be carried out by any known method such as solution polymerization, suspension polymerization, or bulk polymerization, but solution polymerization is particularly superior in terms of control of the degree of polymerization and ease of handling. The polymerization solvent is not particularly limited, but
Methyl alcohol and ethyl alcohol are most desirable from the viewpoint of post-processes such as saponification. To prepare the hot melt adhesive of the present invention,
The copolymer obtained by polymerization has an intrinsic viscosity [η] (in acetone solvent at 30°C, concentration unit g/100ml).
Measured in. ) is 0.09 to 0.35, preferably 0.14 to 0.21. When the intrinsic viscosity is less than 0.09, the intermolecular cohesive force becomes weak and the adhesive strength becomes insufficient.
If it exceeds 0.35, the melting temperature and viscosity will become too high, making it impossible to use an applicator for ordinary hot melt adhesives, which is inappropriate. The degree of polymerization _AC of polyvinyl acetate (hereinafter abbreviated as PVA _c ) having an intrinsic viscosity [η] of 0.09 to 0.35 is 50 or more and less than 450 when calculated from the following viscosity formula. log _AC =1.613 log[η]×10 ⁴ /7.94 The copolymer obtained as above is saponified by a known method. The hot melt adhesive of the present invention is made of a partially saponified copolymer, and the saponification reaction is schematically shown in the following formula. As can be seen from the above equation, the acetate groups in the vinyl acetate and allyl acetate parts of the copolymer are hydrolyzed and converted into hydroxyl groups by the saponification reaction, but the branched fatty acid groups in the vinyl part of the saturated branched fatty acid are not easily saponified due to their steric hindrance. It does not undergo chemical reaction and preferentially remains. The partially saponified product constituting the hot melt adhesive of the present invention is preferably 50 to 85 mol% of the vinyl acetate portion and allyl acetate portion of the copolymer by a saponification reaction.
It has 55 to 70 mol% changed to hydroxyl groups. Generally, the percentage converted to hydroxyl groups is called the degree of saponification, so if expressed in terms of degree of saponification, the degree of saponification of the vinyl acetate portion and allyl acetate portion of the copolymer is 50.
~85 mol%, preferably 55-70 mol%. If the degree of saponification is less than 50 mol%, the water solubility of the partially saponified product tends to be extremely reduced, which is not preferable as a water-soluble or water-dispersible adhesive. If the degree of saponification exceeds 80 mol%, the melting point and melt viscosity of the partially saponified product will become extremely high, making hot melt coating difficult, which is not preferable. Table 1 shows the effects of copolymerization of saturated branched fatty acid vinyl and allyl acetate and the degree of saponification on adhesive performance.

【table】

[Table] As is clear from Table 1, PVA with a low degree of polymerization and low saponification (Sample No. 6) has too high a melting point and a high melt viscosity, so it is not suitable as a hot melt adhesive. Furthermore, when PVA is copolymerized with saturated branched fatty acid vinyl (sample No. 5), the melting point and melt viscosity decrease, but the width is small and insufficient. Furthermore, when allyl acetate is copolymerized with PVA (Sample No. 4), although the melting point and melt viscosity are significantly lowered, "stickiness" occurs at high temperatures, which is not suitable. On the other hand, the adhesives of the present invention, especially the adhesives of Samples No. 1 and No. 2, have appropriate melting points and melt viscosity, are not "sticky" at high temperatures, and are also water-soluble. Therefore, it is particularly preferred as a water-soluble hot melt adhesive, especially a water-soluble rewetting hot melt adhesive. The partially saponified product obtained as described above can of course be used alone as a water-soluble or water-dispersible hot melt adhesive as described above, but it also has excellent heat resistance, cold resistance, and moisture resistance. and thermoplastic resins commonly used as hot melt adhesive components to improve workability.
It is preferable to add tackifiers, waxes, plasticizers, fillers, antioxidants, etc. Examples of thermoplastic resins that can be used include polyethylene, polypropylene, ethylene-propylene copolymer, polyvinyl acetate, ethylene-vinyl acetate copolymer and its derivatives, ethylene-acrylic acid copolymer, and ethylene-acrylic acid ester copolymer. Polymers, ethylene-vinyl acetate-organic acid copolymers, ethylene-propylene-organic acid copolymers and derivatives thereof, polyesters, polyamides, butyl rubber, styrene-butadiene copolymers, styrene-isoprene copolymers, etc. . Examples of tackifiers that can be used include rosin, modified rosin and its derivatives, polyterpene resin, terpene phenol resin, aliphatic hydrocarbon resin, alicyclic hydrocarbon resin, aromatic hydrocarbon resin, styrene resin, xylene resin, coumaron-indene resin, vinyltoluene-α-methylstyrene copolymer, and the like. Examples of waxes that can be used include paraffin wax, microcrystalline wax, low molecular weight polyethylene wax, and oxidized polyethylene wax. Examples of plasticizers that can be used include polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, sorbitol, and mannitol, and modified products thereof; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, and diethylene glycol; Glycols such as propylene glycol, tripropylene glycol, polypropylene glycol and their modified products, urea and ethylene urea,
Examples include urea derivatives such as propylene urea, phthalate esters such as DOP and DBP, and phosphate esters such as TCP and TPP. Further, examples of fillers that can be used include calcium carbonate, barium sulfate, zinc oxide, magnesium oxide, titanium oxide, and hydrated silicic acid. Furthermore, phenol-based, amine-based, phosphoric acid-based, and other antioxidants may be appropriately blended. The above thermoplastic resins, tackifiers, waxes, plasticizers, fillers, and antioxidants can be used alone or in combination of two or more. When the water-soluble or water-dispersible hot melt adhesive of the present invention is used for binding backing books, sealing cardboard or cartons, pressure-sensitive tape, labels, and rewetting tape, and then is recovered as waste paper, in the recovery re-process. There are no problems caused by adhesives. In addition, even in recycled products, there are no small pieces of adhesive left, and unlike recycled products made from waste paper using traditional hot melt adhesives, spots may develop due to the residual adhesive when heated. There's nothing to do. Further, since the adhesive of the present invention is water-soluble and has hot-melt properties, it is also suitable for use as a temporary adhesive interlining for cloth. The adhesive of the present invention has excellent adhesive properties, particularly heat resistance, cold resistance, and moisture resistance, and also has little evaporation during melting, an appropriate melt viscosity, and excellent flexibility. Since it has good thermal stability, it exhibits excellent performance as a hot melt adhesive. Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that "parts" in the examples mean "parts by weight." Example 1, Comparative Examples 1 to 3 Vinyl balsatric acid (manufactured by Ciel Chemical, trade name
Veo Va) 10g, allyl acetate 50g and vinyl acetate 500g in 550g methyl alcohol using 6.0g azobisisobutyronitrile (AIBN) as an initiator.
Polymerization was carried out at 60°C for 5 hours. As a result, the intrinsic viscosity [η] of an acetone solution at 30°C was 0.18 (concentration unit g/
100ml) of copolymer was obtained. This polymerization solution was demonomerized, methyl alcohol was added to adjust the polymer concentration to 63% by weight, and then it was saponified at 40°C using 8 milli equivalents of caustic soda based on the total of the vinyl acetate portion and allyl acetate portion. , a modified PVA in which 65 mol% of the vinyl acetate portion and allyl acetate portion of the copolymer was saponified was obtained. This modified PVA was dispersed in water at 20°C, melted at 108°C, had a melt viscosity of 26,000 centipoise at 200°C, and did not become "sticky" even at 40°C and 80% RH. This modified PVA (Example 1), allyl acetate modified PVA (Comparative Example 1) shown in Table 2 for comparison,
A compatibility test was conducted on Veo Va modified PVA (Comparative Example 2) and unmodified PVA (Comparative Example 3). That is, 100 parts of each of the polymers shown in Table 2 and the respective components shown in Table 3 were mixed at 170°C in the proportions shown in Table 3, and their compatibility was observed. The results are in Table 3
As shown in Figure 1, in Example 1, they were compatible over a wide range, and the compatibility was greatly improved compared to Comparative Example.

【table】

【table】

[Table] Next, each modified PVA and unmodified PVA shown in Table 2
For each 100 parts of PVA, 30 parts of polyethylene glycol (PEG, molecular weight 600) and 10 parts of ethylene-vinyl acetate copolymer (EVA MI 400 VA _c 28 mol%) were added.
An adhesive was obtained by mixing at 180°C. When the obtained adhesive was used as a hot-melt adhesive and the spine was tested by perfect binding, a good binding was obtained. Furthermore, the results of measuring the adhesive strength when using this adhesive were as shown in Table 4. Note that the above adhesive strength indicates the adhesive strength when two sheets of paper are peeled off from a sample cut to a width of 5 cm. Each of the above bound books was put into a waste paper recycling dissociator with water and stirred for 10 minutes. The adhesive was finely dispersed and no solid adhesive was found. This disassembled product was made into paper and heated to 180°C. However, no spots due to residue appeared.

[Table] Example 2 20 g of trimethyl vinyl acetate, 80 g of allyl acetate and 300 g of vinyl acetate were subjected to bulk polymerization at 80° C. for 3.5 hours using 5.5 g of AIBN as an initiator. As a result, the intrinsic viscosity of an acetone solution at 30℃ with a polymerization yield of 80% [η] =
A copolymer with a concentration of 0.32 (concentration unit g/100ml) was obtained. After demonomerizing this polymerization solution, it was dissolved in methyl alcohol to a concentration of 60% by weight, and then saponified at 40°C using 12 milliequivalents of caustic soda based on the total of allyl acetate and vinyl acetate. , a modified PVA in which 80 mol% of the allyl acetate portion and the vinyl acetate portion of the copolymer was saponified was obtained. This modified PVA melts at 121°C, has a melt viscosity of about 100,000 centipoise at 200°C, is dispersed in water at 20°C, is not sticky at all at 60%RH at 20°C, and is not sticky at 40°C.
Even at 80% RH, there was almost no stickiness. Allyl acetate modified PVA (Comparative Example 4) shown in Table 5 for comparison with the obtained modified PVA (Example 2),
A compatibility test was conducted in the same manner as in Example 1 for trimethylvinyl acetate-modified PVA (Comparative Example 5) and unmodified PVA (Comparative Example 6). The results are in Table 6
As shown in , Example 2 had significantly improved compatibility with other resins and plasticizers compared to Comparative Example.

【table】

【table】

[Table] Next, each modified PVA and unmodified PVA shown in Table 5
100 parts each of PVA, 35 parts of diacetin and EVA
(MI400, VA _c 28 mol%) were mixed at 180°C to obtain an adhesive. The obtained adhesive was subjected to a heat seal test and a rewet adhesion test. That is, apply the adhesive in a molten state to a thickness of approximately 200 g/m ² on K-liner paper, cut this K-liner paper into 15 mm width, and then apply another K-liner paper of the same width to the tip 15 mm. A heat seal test was carried out by pressing with an iron at 140°C, and an adhesion test was carried out with another K-liner of the same width after wetting the 15 mm tip with water. The tensile strength was measured using a tensile tester and the results were as shown in Table 7. Further, when a waste paper recovery test was conducted on the above exam subject in the same manner as in Example 1, good results were obtained as in Example 1.

[Table] Example 3 Veo Va (Ciel Chemical) 4g, allyl acetate 20
g and 165 g of vinyl acetate to 200 g of ethyl alcohol.
Polymerization was carried out at 70° C. for 5 hours using 28 g of AIBN as an initiator. As a result, a copolymer having an intrinsic viscosity [η] of 0.095 in an acetone solution at 30°C was obtained. This polymerization solution was desolvented at 120°C to obtain a glassy copolymer, which was then redissolved in methyl alcohol to a concentration of 70% by weight, and then 6 milliequivalents based on the total of vinyl acetate and allyl acetate. The copolymer was saponified at 40℃ using caustic soda, and 60 mol% of the vinyl acetate and allyl acetate portions of the copolymer were saponified.
Got PVA. This modified PVA was dispersed in water at 20°C and melted at 95°C, and the melt viscosity at 200°C was as low as 950 centipoise, but it did not become sticky even under high temperature and high humidity conditions of 40°C and 80% RH. Nakatsuta. Allyl acetate modified PVA (Comparative Example 7) shown in Table 8 for comparison with the obtained modified PVA (Example 3),
A compatibility test was conducted in the same manner as in Example 1 for Veo Va modified PVA (Comparative Example 8) and unmodified PVA (Comparative Example 9). The results are shown in Table 9, and Example 3 had significantly improved compatibility with other resins and plasticizers compared to Comparative Examples.

【table】

【table】

[Table] Next, each modified PVA and unmodified PVA shown in Table 8
An adhesive was obtained by melt-mixing 50 parts of a 6 mole adduct of sorbitol with propylene oxide and 20 parts of rosin to 100 parts each of PVA. Apply the obtained adhesive in a molten state at 160°C to the 15 mm tip of a 15 mm wide K liner paper in an amount of about 100 g/m ² , and while the adhesive is melting, apply the other K liner tip. An adhesion test was conducted by adhering to this. The tensile strength was measured using a tensile tester and the results were as shown in Table 10.

[Table] From the results in Table 10, it is clear that the hot melt adhesive of the present invention can be preferably used throughout the summer and winter. Further, when a waste paper recovery test was conducted on the above sample in the same manner as in Example 1, good results were obtained as in Example 1.

Claims (1)

[Claims] 1 (a) General formula CH ₂ = CHOCOCR ₁ R ₂ R ₃ (however,
R ₁ R ₂ R ₃ represents an alkyl group) 0.5 to 10 parts by weight of saturated branched fatty acid vinyl, (b) 1 to 40 parts by weight of allyl acetate, and (c) 100 parts by weight of vinyl acetate are copolymerized. Intrinsic viscosity obtained by (30℃ in acetone solvent,
A water-soluble or water-dispersible hot melt made of a partially saponified product in which 50 to 85 mol% of the vinyl acetate portion and allyl acetate portion of a copolymer with a concentration unit of g/100 ml are saponified to form hydroxyl groups with a concentration of 0.09 to 0.35. glue.