UA78545C2 - Method for joining wood based materials - Google Patents

Abstract

The present invention relates to a method of joining two or more pieces of wood based materials, comprising the steps of providing at least two pieces of wood based material; separately applying an adhesive composition (A), comprising a curable resin, and a composition (B), comprising a gel forming substance, onto at least one of said at least two pieces; joining the two pieces together to form anassembly having the compositions (A) and (B) situated between the pieces; pre-pressing of the obtained assembly is carried out, with no curing of the resin; and then, hot-pressing the assembly to cure the resin.

Description

Description of the invention

The present invention relates to a method of joining wooden materials, in which an adhesive composition that hardens 2 and a composition containing a gel-forming substance are applied separately to wooden materials.

It also refers to wooden products obtained by the specified method.

Some methods of gluing wood materials include a pre-pressing stage followed by a hot-pressing stage. This is particularly the case in gluing methods such as plywood and laminate veneering, where a thermosetting adhesive is applied to veneers that are collected and 70 usually pre-pressed at room temperature to form a veneer package. The package is then usually pressed by hot pressing, where the glue hardens. It is important that the veneers sufficiently adhere to each other after the preliminary pressing stage so that the package does not collapse with the destruction of its shape.

If the veneers do not sufficiently adhere to each other, the package may also be dented in the hot pressing equipment. Therefore, poor cold adhesion leads to the fact that some material cannot be used 719 after pre-pressing, thus creating waste.

When preparing the recipe of a typical curing glue, usually various impurities are mixed with the curing resin. Impurities usually affect shelf life, which can be reduced from up to several weeks for resin alone to only a few days or less for a fully formulated, curable adhesive composition. Some impurities lead to very short lifetimes, causing recycling problems.

Thus, problems of very low viability are often present in the formulation of adhesive compositions.

To improve cold adhesion, admixtures such as grain-based materials, including wheat flour, corn flour, etc., are commonly used as components in curing adhesive compositions.

However, grain-containing admixtures can be used only up to a certain amount without too much thickening of the adhesive composition. In addition, various natural or synthetic polymers were investigated, but without obtaining any satisfactory improvement. Thus, the characteristics of known admixtures for improving cold adhesion are insufficient, and there is a need to improve cold adhesion when joining wood materials without the problems of very low viability.

When gluing two surfaces together, there is a certain maximum allowable assembly time, that is, the maximum length of time between the application of adhesive components and the joining of parts, for example in a press. The assembly time of 30 should be long enough to ensure the assembly and adjustment of the glued parts in a practical way. "AND

In MO 89/05221| the method of obtaining wooden products is described, where the hardener is used in the zone of the separated edges of the veneer layer. However, due to the use of a rapid hardener, the assembly time to o pre-pressing is very short. Also, the method according to (M/O 89/05221| can lead to dispersion of the quality of the adhesive connection between different parts of the adhesive connection and large waste. 325 In Ipatent US Mo4824896)| described glue for connecting wooden parts of high moisture content, which - optionally, includes borax. US Pat. No. 2,889,2411 discloses a phenolic resin composition containing a boronic acid compound such as boric acid. US Pat. " or EP 0259042 ALI cold adhesion is not disclosed. With 70 The object of the present invention is to provide a method of joining wood materials that gives excellent cold adhesion, minimizes viability problems and allows sufficient time for assembly. The method is acceptable for methods where with" a curing adhesive composition is used, which includes a pre-pressing stage and a hot-pressing stage. Another object of the present invention is to create wooden products obtained by the specified method. 45 According to the present invention, the possibility of achieving the above-mentioned objects by this method was found. connecting two or more pieces of wood materials, comprising the steps of: o (a) providing at least two pieces of wood materials ialu; (B) separate application of the adhesive composition (A), which contains a curing resin, and the composition (B), and which contains a gelling substance, on at least one of the specified at least two parts; "Iz" 20 (c) connection of two parts together with the formation of a package having compositions (A) and (B) located between the parts; (4) preliminary pressing of the received package without curing the resin; and then sl (e) hot pressing of the package with resin curing.

According to this invention, it was also found possible to achieve the above-mentioned tasks by connecting two or more parts of wood materials, which includes the stages: (a) providing at least two parts of wood material;

GF) (B) separate application of the adhesive composition (A), which contains a resin that hardens, and the adhesive composition (B), which contains a non-hardening gelling agent, to at least one of the specified at least two parts; (c) joining the two parts together to form a package having the compositions (A) and (B) located between the parts; 60 (a) preliminary pressing of the received package; and then (is) hot pressing the package with curing resin.

By "gelling substance" is meant a substance which itself or its derivatives are able to cause gelation of the adhesive composition (A) according to the present invention, but not to cause a significant hardening of the adhesive composition (A) at a relatively low temperature in the process of preliminary pressing, for example when room temperature 20-252C, which is an example of a temperature interval in the process of preliminary pressing.

By "curing" the resin is meant the transition of the curing resin into a cured cross-linked essentially solid state.

By "pre-pressing" is meant pressing at a temperature below the required curing temperature of the applied thermosetting adhesive composition, so that no significant curing takes place during the pre-pressing.

"Cold adhesion" refers to adhesion after pre-pressing between two surfaces that have a thermosetting adhesive layer between the surfaces.

By "hot pressing" is meant pressing at a temperature higher than the temperature at 7/0 pre-pressing, at or above the required curing temperature of the applied thermosetting adhesive composition, so that the adhesive is cured.

A suitable curable adhesive composition (A) according to the present invention includes any curable adhesive composition which requires an increase in temperature to cure sufficiently rapidly.

Adhesive composition (A) may contain more than one resin. An acceptable adhesive composition (A) contains a phenolic 7/5 bMmol or a combination of an amino resin and a non-curing resin.

Phenolic resins are condensates of various phenolic compounds and aldehydes. The phenolic compound can be phenol itself, polyatomic phenols and alkylphenols such as resorcinol, alkylresorcinol, cresols, ethylphenol and xylenol, and naturally occurring phenolic compounds such as tannins. Examples of suitable aldehydes include formaldehyde, acetaldehyde, glutaraldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde and furfural. The phenolic resin can exist as a solution in water or an alcohol such as ethanol. Accordingly, phenolic resin exists as an aqueous solution with varying dry resin content. The phenolic resin used in the adhesive composition (A) according to the present invention is preferably a phenolic resin containing formaldehyde, such as phenol-formaldehyde resin, resorcinol-formaldehyde resin, and phenol-resorcinol-formaldehyde resin. Preferably, the adhesive composition (A) contains phenol-formaldehyde resin. The dry resin content of the phenolic resin is preferably from about 20 to about 8095 wt, more preferably from about

ZO to about 6095 wt.%, and most preferably from about 40 to about 5095 wt.%, wherein the other portion of the resin is preferably essentially water. The molar ratio of formaldehyde to the total amount of phenolic compounds (to one or both of phenol and resorcinol) when preparing the resin is, respectively, from about 0.1 to about 0.4 for phenol-resorcinol-formaldehyde resin, preferably from about 0.5 to about 1. For a phenol-formaldehyde resin, the mole ratio of phenol to formaldehyde is preferably from about 1 to about 3.

Amino resins are condensates of carbonyl compounds, such as aldehydes, with compounds containing amino, imino, or amido groups, such as urea, melamine, thiourea, guanamines, ethylene urea, cyanamide, dicyandiamide, and guanidine. Amino resins are mainly formaldehyde condensates and compounds containing amine, among which the most common are urea and melamine, which give urea-formaldehyde and melamine-formaldehyde, and melamine-urea-formaldehyde. The amino resin used in the adhesive composition (A) according to the present invention is acceptable urea-formaldehyde resin or melamine-formaldehyde resin. The dry content of the resin in the amino resin is, respectively, from about 30 to about 9095 by weight, preferably from about 45 to about 8095 by weight, most preferably from about 55 to about 7595 by weight, and the other part of the resin is preferably essentially water . The resin, which does not cure, is preferably a polymer containing polar groups, preferably polymers of complex vinyl ether or its derivatives, most preferably polyvinyl acetate or polyvinyl alcohol. The amount of non-curable resin in the adhesive composition (A), respectively, is from about 0.1 to about 4095 mass, preferably from about 0.5 to about 3095 mass, more preferably from about 1 to about 1595 mass, the most preferably, from about 2 to about 1095 wt.%, calculated as the dry matter of the non-I-curable resin, in the entire non-cured adhesive composition (A). Amino resin is accordingly cured using traditional hardeners at elevated temperatures, respectively above 502C, preferably above 8096. The recipe of the adhesive composition (A) can be made in any acceptable way according to the existing state of the art. A suitable adhesive composition (A) may contain various additives such as curing catalysts and fillers such as nut shell flour or other starch-containing substances known in the art. The appropriate viscosity of the adhesive composition (A) when applied to the surface of wooden materials depends on the method of application used. The adhesive composition (A) accordingly has a viscosity of

Brookfield at 252 from about 100 to about 150,000 spz, preferably from about 300 to about 50,000 spz.

The gelling substance is preferably a non-curing substance, which means that the curable adhesive composition containing the substance does not cross irreversibly at 20 C even after several hours. Examples of suitable gelling agents according to the present invention include inorganic and organic gelling agents. Inorganic gelling substances 60 include boron-containing compounds and metal ions. The boron-containing compound according to this invention preferably contains oxygen, most preferably, the boron-containing compound is selected from the group of boric acid, borate salts, or combinations thereof. Borate salt here includes all types of borate salts such as metaborates, triborates, tetraborates, etc. The boron-containing compound is accordingly soluble in water or organic solvents such as glycerol, ethylene glycol, diethylene glycol, methanol or ethanol. Preferably, the boron-containing compound dissolves in water. Metal ions 65 preferably belong to group ZA or are metal ions belonging to any of groups 38-88 of the periodic table of elements, such as zinc, zirconium and chromium. Metal ions dissolve in water accordingly. If one or more gelling agents are used, the composition (B) contains one or more gelling agents respectively in an amount to saturate the gelling agent or agents in the solvent used, respectively from about 0.01 to about 5095 wt, preferably from about 0.1 to about 3095 wt., more preferably from about 0.5 to about 2595 wt., most preferably from about 1 to about 2095 wt.

Organic gelling substances according to this invention include compounds having an ester functional group. An organic gelling agent is acceptable when the phenolic resin is used in the adhesive composition (A). Acceptable such a gelling substance is selected from the group 7/0 consisting of esters, lactones, organic carbonates or mixtures thereof. Acceptable esters include (but are not limited to) methyl formate, methyl acetate, ethyl acetate, N-butyl acetate, butylene glycol diacetate, ethylene glycol diacetate, and glycerol triacetate (triacetetin). Other complex aliphatic C4-C monoesters can also be used, such as methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, butyl acetate, propyl acetate, methyl propionate, ethyl propionate, /5 propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl pentanate, ethyl pentanate , propylpentanate, butylpentanate. Multiethers such as ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, propylene glycol dialkyl ether, butylene glycol dialkyl ether, glycerol alkyl ether, 1,3-propanediol alkyl ether, 1,3-butanediol alkyl ether, 1,4 -butanediol alkyl ether, where the alkyl represents Co 4-C. Suitable organic carbonates include (but are not limited to) propylene carbonate, ethylene glycol carbonate, glycerin carbonate, 1,2-butanediol carbonate, 1,3-butanediol carbonate, 1,2-pentanediol carbonate, 1 ,3-pentanediol carbonate. Preferably, propylene carbonate is used. Lactones include (but are not limited to) gamma-butyrolactone, beta-propiolactone, beta-butyrolactone, beta-isobutyrolactone, beta-isopentylactone, gamma-isopentylactone, and delta-pentylactone. When an organic compound, such as a compound having an ester functional group, is used as the gelling agent, the composition (B) accordingly contains from about | to about 10095 wt., preferably from about 10 to about 4095 wt., gelling agent. The first part of the composition (B) is mainly essentially water.

The acceptable Brookfield viscosity of the adhesive composition (A), gelled with a gelling agent at 202C, decreases when the gel is moderately heated, for example to 50C. This indicates that the gelation is reversible and that significant irreversible crosslinking of the adhesive composition (A) does not occur. in

The mass ratio of the applied adhesive composition (A) to the applied composition (B) is from about 100:1 to about 2:1, preferably from about 50:11 to about 5:1, most preferably, from about 30:1 to about 10:1, calculated per unit area. co

Application of adhesive composition (A) and composition (B) can be done in any order of application. uh-

Preferably, the adhesive composition (A) is applied to the surface of the composition (B). Application of the adhesive composition (A) and composition (B) to the wood material can be performed using any acceptable method known in the art, such as spraying, brushing, extrusion, roller application, bulk application, etc., with obtaining such forms as drops, one or more threads, balls or essentially a continuous "layer. Preferably, the adhesive composition (A) is applied using methods of extrusion, roller application or bulk application, while composition (B) is preferably applied by spraying. y Preferably, from about 20 to about 10095 of the surface subjected to application of the adhesive composition (A), y? is subjected to application of composition (B), more preferably from about 50 to about 10095, most preferably from about 80 to about 10095. By "surface subjected to application" is meant a surface subjected to any method of application without requiring some degree of coating any composition -And (A) or (B).

In the method according to the present invention, two or more parts of wood materials are joined, forming a package of parts, which is subjected to the stage of pre-pressing, respectively, at an ambient temperature of about 0°C, preferably from about 0 to about 402C, most preferably from about 5 to about 3090. The pre-pressing stage according to this invention is preferably carried out at a pressure of from about 1 to about 5 kg/cm2, more preferably from about 2 to about 25 kg/cm2, most preferably from about 4 to about 15 kg/cm2. The pre-press time depends on the resin used and the type of package being pressed, and is preferably from about 0.1 to about 30 minutes. For the phenolic resin, the prepress time is preferably from about 0.1 to about 15 minutes, even more preferably from about 1 to about 10 minutes, most preferably from about 3 to about 5 minutes. For amino resin

Gee! the pre-pressing time is preferably from about 5 to about 30 minutes, most preferably from about 8 to about 15 minutes. The package of parts is additionally subjected to the stage of hot pressing, which is carried out at a temperature at or above the temperature of hardening of the adhesive composition (A). The hot pressing step according to this 60 invention is preferably carried out at a pressure of from about 1 to about BOkg/cm2, more preferably from about 2 to about 25 kg/cm , most preferably from about 4 to about 15 kg/cm7. The temperature at the hot pressing stage depends on the resin used and is preferably from about 50 to about 2002C. For phenolic resin, the hot pressing temperature is preferably from about 80 to about 2002C, more preferably from about 120 to about 1702C. For the amino resin, the hot pressing temperature 65 is preferably from about 50 to about 1502C, more preferably from about

90 to about 1302C. The time of hot pressing depends on the resin and the thickness of the package and is preferably from about 0.01 to about 5 minutes. per mm of the thickness of the package, more preferably, from about 0.1 to about 2 min. per mm of the thickness of the package, most preferably, from about 0.2 to about 1 min. per mm of the package thickness.

In one preferred embodiment of the invention, a curable adhesive composition containing a phenolic resin is applied to a layer of wood, after which a composition containing boric acid is applied to the applied adhesive composition. Two or more layers are pre-pressed to obtain a package, which is then pressed by hot pressing with hardening as a result of the adhesive composition.

In another preferred embodiment of the invention, a curable adhesive composition containing a combination of 7/0 amino resin and polyvinyl ether is applied to the layers of wood, after which a composition containing boric acid is applied to the applied adhesive composition. Two or more layers are pre-pressed to obtain a package, which is then pressed by hot pressing with hardening as a result of the adhesive composition.

Wood materials according to the method according to the invention can be of any type, which can be connected by an adhesive system. Preferably, the wood materials are veneers or other wood sheets.

The wood products obtained by the method according to the present invention can be of any type where the hot pressing step is acceptable, examples of such products are plywood, layered facing material and flooring materials.

The invention below will be further described by the following examples, which, however, should not be interpreted as limiting the scope of the invention.

Examples

Example 1

The method according to this invention is tested by gluing veneers into a two-layer plate with a standard adhesive composition obtained with 100 wt. phenol-formaldehyde resin, 1 wt.h. sodium carbonate, 9 wt.h. wheat flour and 5 wt. water The resin has a dry content of 4595 wt. The recipe of the adhesive composition has p

VISCOSITY According to Brookfield at 25923 about 3000 spz. The tested veneers are Kadaia (a-pine with a thickness of Zmm.

The adhesive composition is applied by extrusion in a thread in the amount of 220 g/m?. The composition (B) according to the present invention is obtained, containing about 595 wt. sodium tetraborate decahydrate and about 9595 wt. water

The composition (B) is sprayed onto the applied adhesive composition in the amount of approximately 10 g/m. Hot pressing is carried out at a pressure of 10 kg/cm2 at a temperature of 21-259C for a second. Three t) identical experimental plates are obtained and tested. The amount of surface on the upper part and the lower part of the two-layer plate, "E which separated from each other ("disconnected"), is registered through ЗОхв. A separation value of 10095 means complete separation, while 09o means the layers are glued together. Shit

Fo and -

3 min. (95) quiche h | Average | C - The experiment is performed as in example 1, but without spraying the composition (B) on the applied glue. and? ev - so 2 7177 OSerednk ev y y t. It can be concluded that the separate application of components according to this invention gives a significant improvement in cold adhesion.

Example 2

Samples of phenol-formaldehyde resin ((PE) (FF)) and combinations of urea-formaldehyde resin (P) (SF)) and polyvinyl alcohol (PmAI) (PVA)) are tested with a gelling agent according to this invention and citric acid as a hardener ( for SF) in accordance with (MO 89/05221). 15 g of the composition containing (F) or 1095 wt. gelling substance, or 2095 wt. hardener in accordance with (MO 89/052211, g is mixed with 180 g of glue containing either FF resin or the SF/PVA resin system. The SF/PVA system also contains a traditional hardener, and the ratio of components is 100 parts by mass of SF, 6 parts by weight of PVA (1795 parts by weight) and 20 boron/part by weight of hardener. The mixture is then held for 1 minute at 202C, after which the appearance and viscosity are recorded. The temperature is then rapidly raised to about 50 2C, and again record the appearance and viscosity of the sample 65 Brookfield viscosity and/or appearance

209c BOS

I he innnsiao "SNY SHNSHE - From Yaiznnan (solid gel)

It can be concluded that gelling substances according to this invention do not cause 70 irreversible crosslinking of resins at room temperature. In addition, the combination of hardener citric acid/aluminum sulfate according to (MO 89/052211| with SF/PVA gives a hard gel after 1 min. at 209С, which does not soften when heated, which indicates irreversible hardening.

Claims (11)

The formula of the invention 1. The method of connecting two or more parts of wooden materials, containing the following stages, in which: (a) provide at least two parts of wooden materials; (B) carry out separate application of the adhesive composition (A), which contains a curing resin, and the composition (B), which contains a gelling substance, on the surface of at least one of the specified at least two parts; and the mass ratio of the adhesive composition (A), which is applied, to the composition (B), which is applied, is from about 100:1 to about 2:1, per unit area; (c) connect two parts together to form a package containing compositions (A) and (B) located between c parts; o (4) carry out preliminary pressing of the received package without curing the resin; and then (e) hot-pressing the resin-cured bag. 2. The method according to claim 1, which differs in that the adhesive composition (A) is applied to the composition (B). 3. The method according to any of claims 1-2, which differs in that the wood material is veneer. IC o) 4. The method according to any one of claims 1-3, which is characterized by the fact that an adhesive composition (A) containing phenolic resin is used. WITH 5. The method according to any of claims 1-3, which is characterized by the fact that the adhesive composition (A) is used, which IS o) contains a combination of polyvinyl acetate or polyvinyl alcohol and amino resin. b. The method according to claim 5, which differs in that the amino resin is urea-formaldehyde resin or 09 melamine-formaldehyde resin. - 7. The method according to any one of claims 1-6, which is characterized by the fact that the gel-forming substance is boric acid, borate salt or their combination. 8. The method according to claim 4, which is characterized by the fact that the gel-forming substance is a metal ion belonging to group "ZA" or a transition metal ion belonging to any of groups 38-88 of the periodic system of elements. 9. The method according to any one of claims 7 or 8, which is characterized by the fact that the composition (B) contains from about 0.5 to about 95 wt. gelling substance. and 10. The method according to claim 4, which is characterized by the fact that the gel-forming substance is selected from the group consisting of "" esters, lactones, organic carbonates or their mixtures. 11. The method according to claim 10, which is characterized in that the composition (B) contains from about 10 to about 40 90 wt. gelling substance. -| 12. The method according to any one of claims 1-11, characterized in that the mass ratio of the applied adhesive composition (A) to the applied composition (B) is from about 30:1 to about 10:1 , calculated per unit area. 1 13. A wooden product obtained by the method according to any of claims 1-12. iz 50 14. A wooden product according to claim 13, which is plywood, layered facing material or material for flooring. sl Official Bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated microcircuits", 2007, M 4, 15.04.2007. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. F) name) 60 b5