JPS6012379B2 - Component adhesive based on polyvinyl ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a one-component adhesive with good water resistance and storage stability, consisting of an aqueous polypinyl ester dispersion, a urea-formaldehyde resin and an acidic metal salt.

Polyvinyl ester type adhesives are known.

They are used as solutions, as melt adhesives or in the form of aqueous polymer dispersions. A disadvantage of this dispersion adhesive is its low water resistance, influenced by the presence of water-soluble dispersants such as emulsifiers and protective colloids in the aqueous dispersion. Water resistance can be improved by adding urea resin [E.Rakness]
nes)'s "HolzalsRoh" plate dWerksto
ffzo, volume 19 (1961), pages 239-24).
However, such mixtures are unstable and have limited storage stability of up to one week. Furthermore, in most cases hardeners must also be used. German Patent Application No. 1,594,194 discloses that an aqueous polyvinyl acetate dispersion containing polypinyl alcohol is treated with an acidic metal salt as a hardening agent, and a water-resistant and far-curable binder mixture is known to be obtained.

However, this mixture has a storage stability of only a maximum of 4 glue hours. The present inventor has proposed that in a one-component adhesive based on an aqueous polyvinyl ester dispersion containing polyvinyl alcohol as a protective colloid, the adhesive has a water-soluble low condensation content of 1.5 to 3% by weight. Aqueous solution of urea-formaldehyde resin (resin amount 40-7% by weight)
) and 0.05 to 0.3% by weight of a water-soluble acid salt of aluminum or chromium, it has been found that high water resistance and good storage stability are exhibited.

The aqueous polyvinyl ester dispersion may be a homopolymer of vinyl ester or a copolymer of vinyl ester itself or of vinyl ester and other ethylenically unsaturated monomers, in which case the proportion of incorporated vinyl ester in the polymer is at least A polymer dispersion of -5% by weight is suitable.

Vinylesters include pinylesters of saturated aliphatic monocarboxylic acids having 1 to 18 C atoms, such as vinyl-formate, vinyl acetate, vinyl propionate, vinyl isoptylate, vinyl laurate, etc. Vinyl esters or vinyl stearates of branched saturated monocarboxylic acids having C atoms of are suitable, in particular vinyl acetate. Other ethylenically unsaturated monomers that can be copolymerized with pinylester include esters of acrylic or methacrylic acid or these with monohydric saturated aliphatic alcohols having 1 to 8 carbon atoms, maleic acid, fumaric acid, etc. acids, mono- or di-esters of Q,8-ethylenically unsaturated dicarboxylic acids such as itaconic acid or citraconic acid with monovalent saturated aliphatic flucols having 1 to 8 C-atoms, ethylenic Unsaturated hydrocarbons, such as ethylene, Q-olefins with 3 to 12 C atoms, styrene, vinyltoluene or vinylxylene, halogenated unsaturated aliphatic hydrocarbons, such as vinyl chloride, vinyl fluoride, vinylidene chloride or vinylidene. fluoride and nitrogen-containing derivatives of acrylic or methacrylic acid, such as acrylonitrile, acrylamide or N-methylolacrylamide. The aqueous polyvinyl ester dispersion may optionally contain crosslinking monomers having at least two ethylenic double bonds in the molecule, such as diallyl phthalate, diallyl maleate, triallyl cyanurate, tetraallyloxy Ethane, divinylbenzole, butanediol-1,4-dimethacrylate or triethylene glycol-dimethacrylate or the like may be incorporated and polymerized into the polymer up to 1% by weight based on the total amount of all monomers. The aqueous polypinyl ester dispersions according to the invention additionally contain from 1 to 15% by weight, in particular from 4 to 1a, % by weight, based on the polymer, of polyvinyl alcohol as a protective colloid. The polypynyl alcohol can be added before, during or after the polymerization. In order to obtain certain application properties of the adhesive, such as opening time, curing time, adhesion strength and temperature stability, it is currently advantageous to use mixtures of various aqueous polyvinyl ester dispersions. Particular preference is given to using aqueous polyvinyl ester dispersions, especially homopolymeric polyvinyl acetate dispersions. The solids content of the aqueous polyvinyl ester dispersion is about 40-6% by weight. The aqueous polypinyl ester dispersion is produced in a known manner by free-radical polymerization of the monomers in the aqueous dispersion.

The water-repellent urea-formaldehyde resin with a low degree of condensation contains urea and formaldehyde in a ratio of 1:1 to 1:4, especially 1:2.
obtained by condensation in a molar ratio of ~1:3, 40
It is in the form of an aqueous solution with a resin content of ~7% by weight.

This solution consists of a simple methylol urea compound, i.e. mono-
, di-, tri-, and tetramethylol urea. The adhesive according to the invention contains about 1.5 to 3% by weight of a low degree of condensation urea-formaldehyde resin aqueous solution, based on the total mixture. As the acidic metal salt, an aluminum or chromium salt that reacts with polyvinyl alcohol is used.

Aluminum nitrate, chloro(m)-nitrate are suitable, and aluminum chloride is particularly preferred. The amount added is 0.05 to 0.05 to the total mixture. Box weight% (solid content) or 10% aqueous solution 0.5-3% by weight
It is. Furthermore, in order to improve the film formation of the adhesive at room temperature, known film-forming aids, such as glycolic acid butyl ester or putyl diglycol acetate, may be added in an amount of about 1 to 3% by weight, based on the total mixture. I can do it.

With the one-component adhesive according to the invention, wood and paper bonds are obtained which can be stored for a relatively long time in a humid room or in cold water without the bond loosening.

For such purposes, aqueous polyvinyl ester dispersions have hitherto been either completely unsuitable or suitable only as two-component systems. This is not possible with conventional aqueous polypinyl ester dispersions and can only be accommodated in two-component systems. The storage stability of the adhesive is at least one year without a decrease in its usability, which corresponds to the storage stability of known dispersion adhesives. It also retains the advantageous properties of conventional preferred dispersion adhesives such as long open times, short cure times, high adhesion and good temperature stability of the bond points. Furthermore, the adhesive according to the invention is also suitable for gluing pressed layers, foams, fibres, leather, asbestos and other porous materials, etc. The present invention will be explained in detail in the following examples.

Example 1 Homopolymer polyvinyl acetate 5 containing 7% polyvinyl alcohol as protective colloid
An aqueous dispersion with a weight percent concentration of 95% by weight is prepared.
．． To 5 parts by weight, 1.5 parts by weight of a 50% by weight aqueous solution of a urea-formaldehyde resin with a low degree of condensation is added.
After good dispersion, 1.5 parts by weight of glycolic acid butyl ester and 1.5 parts by weight of a 10% aluminum chloride aqueous solution as a film-forming agent are added while being concentrated in the same manner.
Then homogenize for a further 20 minutes. The rotational speed of the flywheel is about 30 to 50 revolutions/minute. The adhesive thus obtained is subjected to the following adhesive test after at least two unique aging times.

First, in order to test the water resistance of the dried coating,
．． Flow coat the adhesive onto the glass bevel through a fixed slit on the third side. After a drying time of 6 days at a room temperature of 2°C and a relative humidity of 50%, the dried coating is placed in water.

Storage time is 2 hours. The coating does not become white and does not re-emulsify in water. Example 2 Spots. 57.5 parts by weight of a homopolymeric polyvinyl acetate 5 aqueous dispersion containing 10% polyvinyl acetate as protective colloid,
1.5 parts by weight of a 1.6% strength by weight aqueous dispersion of homopolymeric polyvinyl acetate 5 with 5% polyvinyl alcohol as protective colloid, 1.6 parts by weight of a urea-formaldehyde resin 5 with a low degree of condensation. An adhesive prepared in the same machine as in Example 1 from parts by weight of a 10% aqueous solution of aluminum nitrate and 1.5 parts by weight of butyl glycolate is poured into a film.

For comparison, a homopolymer polypynylacetate aqueous dispersion having a solids content of 5% by weight and containing 5% polyvinyl alcohol as a protective colloid is similarly treated. Before making the film, a little water is added to the adhesive according to the invention and to the comparative dispersion to remove bubbles. The weighed amount is poured onto a flat polyethylene ramp with a surrounding enclosure to obtain a film with a dry coating thickness of 0.8 degrees. 2 ○, 5 of these films
The air is conditioned to 0% relative humidity and left for 7 days. The water absorption of this film was determined by placing it in water at 20°C and then weighing it after standing in water for 1 min, 6 min, 120 min, 24 min and 2 min.
As shown in the following table, it is very stable in water compared to that of the comparative dispersion.

Table 1 Example 3 Adhesive, 93. 3. parts by weight of a homopolymeric polyvinyl acetate 5 aqueous dispersion containing 7% polyvinyl alcohol as protective colloid; Parts by weight of
Produced in the same manner as in Example 1 using a weight percent solution of urea-formaldehyde resin 5 with a low degree of condensation, 2.5 parts by weight of a 10% aqueous solution of chromium (m) nitrate, and 1.5 parts by weight of glycolic acid butyl ester. .

A comparative adhesive in the form of this adhesive and a known homopolymer aqueous polyvinyl acetate dispersion having a solids content of 5% by weight and containing 5% polyvinyl alcohol as a protective colloid. Regarding the bond strength,
Tests are carried out in accordance with DW 53254 using test specimens made of beech wood.

The test specimens were produced as follows: two joining members made of beech wood were joined in accordance with the provisions of this DIN.

This joining part has a length of at least 600 ribs and 13
It has 0 ribs. The thickness of this member is 5 mm.
Apply adhesive to both parts. Coating thickness is 150mm/
It is an enemy. Both members are then joined together at a compressive pressure of about 1:1. Compression time is 2 hours. These test specimens are tested for water resistance according to storage series 1, 4 and 5 according to DIN marking 2W.

Storage series 1 consisted of leaving the specimen under air conditioning for 7 days at 20qo and 65% relative humidity, and storage series 4 also consisted of leaving the specimen under air conditioning for 7 days at 20qo and 65% relative humidity. and then submerged in water for 2 hours. On the other hand, storage series 5 is further 20℃
, and then left again under air conditioning at 65% relative humidity for 7 days. The bond strength after storage series 5 is also called the re-drying strength. The results obtained are shown in Table B below.
Table 0 The bond strength bonded with the adhesive according to the invention can still be measured after 24 hours of underwater discharge, whereas the test specimens with the comparative adhesive crumble in water.

The redrying strength of the specimens with the adhesive according to the invention approaches the initial bond strength value (after storage series 1).
Example 4 Experiment No. 4 consisting of the composition shown in Table m. Adhesives Nos. 1 to 6 are manufactured on the same machine as in Example 1.

However, experiment no. Adhesives Nos. 4 to 6 were manufactured for comparison with those of the present invention. A water resistance test was conducted on the same machine as in Example 1, and the results are shown in Table m.

The bond strength test is carried out according to DIN bulb 254 as follows using test specimens prepared as in Example 3:
After standing for 7 days at 23° C. and 50% relative humidity, a 2q hard specimen was cut from the thus bonded Miyakomura.

This specimen has a length of 15 mm and dimensions of 20 mm. Next, these test specimens were divided into 20×10 (
(etc.) Cut across the edge of the tree so that the test surface is exposed. The scale breaking strength is measured by a tensile test according to D River 53254. That is, the specimen is pulled until it breaks, and the maximum load force at that time is measured. Separately, the test specimen is left in water, and after 2 hours it is removed from the water and immediately thereafter subjected to the same tensile test.

The bonding strength of the test specimen is calculated according to the following formula: Funaiso Jawsagi Sardine of the test specimen (N side (Note) IN'Kyo; 0.102 kg/
Iso: 10.2k9/fence The results are shown in Table M.

From Table M of Sohiranuka, it can be seen that the coating films of all adhesives containing metal salts do not re-emulsify and are good in terms of water resistance.

Furthermore, it can be seen that there is no substantial difference in dry bond strength at 23oo between the coating films. The slight variations in the measurements in this test depend on the strength of the respective trees used in the test. Moreover, in tests of bond strength after the specimens had been stored in water for 2 hours, it was found that the adhesive without added metal salts no longer had any strength;
Very good results have been obtained with chromium and aluminum salts.

This effect is exceptionally superior to that of the adhesive using zinc salt used in the adhesion technique (Samurai Ko Sho 44-129596). As can be seen, the adhesives of the invention using chromium and aluminum salts are as good in terms of water resistance, dry bond strength and storage stability as the zinc salts used in the conventional art. In addition, the bond strength after being stored in water for two hours was far superior to that of zinc salts, which showed some effect, and such an effect was completely unexpected from conventional technology. .

The present invention relates to an adhesive described in the claims, and includes the following embodiments.

'11 The adhesive according to the claims, which contains 1 to 15% by weight of polyvinyl alcohol based on the polymer component of the dispersion.

[21] The adhesive according to claim 1 and item ``1'' above, wherein the polyvinyl ester dispersion contains at least 5% by weight of incorporated polymerized vinyl esters based on the polymer component. . '3} In the adhesive described in the claims and the above-mentioned items m to (2), the above-mentioned adhesion agent uses a polyvinyl acetate dispersion as the polyvinyl ester dispersion.

Claims (1)

[Claims] 1. A one-component adhesive based on an aqueous polyvinyl ester dispersion containing polyvinyl alcohol as a protective colloid, in which the adhesive contains urea and formaldehyde in a molar ratio of 1:1 to 1:4 and An aqueous solution (resin content 40-70% by weight) of a water-soluble condensed degree urea-formaldehyde resin consisting of mono-, di-, tri- and tetra-methylol urea (resin content 40-70% by weight) and a water-soluble solution of aluminum or chromium. Acid salt 0.05
Storage-stable one-component adhesive based on the polyvinyl ester described above, characterized in that it contains ~0.3% by weight.