TWI432541B - Method for fabricating environment-friendly starch-based adhesive - Google Patents

Description

Environmentally friendly starch glue preparation method

The invention relates to an environment-friendly glue, and in particular to a formaldehyde-free environment-friendly starch glue.

At present, in the fields of wooden furniture and building materials, fine wood boards and house decoration, urea formaldehyde glue is often used as a glue, but this glue will continuously disperse formaldehyde which is toxic, thereby affecting the health of the human body. In view of this, there are already Many countries have announced the requirement for formaldehyde content control for indoor plywood. In order to comply with national standards, many environmentally friendly adhesives have been developed.

Chinese patent CN 1462786 proposes a preparation method of natural non-toxic adhesive, which is composed of main materials, reinforcing agents, stabilizers and other auxiliary agents. The preparation process requires three chemical modification procedures and one crosslinking procedure, and finally obtains Non-toxic adhesive.

Chinese patent CN 10105034 proposes a preparation method of environmentally friendly adhesive for wood processing, which uses natural polymer bismuth powder and non-toxic organic high molecular weight polyvinyl alcohol as raw materials, and is chemically reacted to form an environmentally friendly adhesive.

Chinese patent CN 1962787 proposes a starch adhesive which first gelatinizes the starch and then chemically reforms the polyvinyl alcohol and butadiene, and then adds urea to improve the adhesive strength, water resistance and flexibility of the adhesive. Make it an environmentally friendly glue for wood.

However, the preparation process of the above-mentioned environmentally friendly adhesive is cumbersome and needs to be combined with liters. Cooling and chemical upgrading procedures make cost prices impossible to reduce. Therefore, the industry is in urgent need of developing a low-cost, formaldehyde-free environmentally friendly adhesive.

The invention provides an environment-friendly starch glue comprising: component A comprising an unmodified original starch; component B comprising a water soluble polymer, an emulsifier and water; and component C comprising a crosslinking agent .

The above and other objects, features, and advantages of the present invention will become more apparent and understood.

The invention provides an environment-friendly starch glue comprising: three components: A, B and C. Since the main raw material of the conventional urea formaldehyde cement is a petrochemical product, it may cause harm to the environment. Therefore, the main raw material component A of the present invention selects unmodified raw starch, such as corn starch, potato starch, rice starch, wheat starch, and tree. Potato starch, which is not only environmentally friendly but also easy to obtain. It should be noted here that the native starch refers to the starch obtained naturally, which has not been modified by any chemical reaction. The component B of the present invention comprises a water-soluble polymer, an emulsifier and water, and the water-soluble polymer comprises a polypolyol or a polyenamine such as polyethylene glycol (PEG) or polytetramethyl ether glycol ( Polytetramethylene ether glycol, PTMEG), polyvinyl alcohol (PVA), polyethylene imine, polyallylamine (PAA). Since the conventional glue contains formaldehyde, it will cause harm to the human body, so the water-soluble polymer containing no formaldehyde is selected; and the emulsifier is a water-insoluble resin, including natural rubber. Glue, styrene, vinyl acetate, acrylic resin, polyurethane or epoxy resin, the role of the emulsifier is to mix the water-soluble polymer and the cross-linking agent evenly when the three components A, B and C are mixed. . Component C of the present invention includes a crosslinking agent such as melamine, trimethoxy melamine, triethoxy melamine, hexamethoxy melamine, hexaethoxy melamine ( Hexaethoxy melamine), this crosslinker is mainly crosslinked with a water-soluble polymer to make it a stable polymer.

The component B of the present invention further comprises a catalyst, which is a weak acid solution, including a solution of citric acid, boric acid, oxalic acid or phosphoric acid. These catalysts can increase the reaction rate and accelerate the crosslinking agent when the three components A, B and C are mixed. Cross-linking reaction with water-soluble polymer. Finally, the three components A, B and C are uniformly mixed to obtain an environmentally-friendly starch cement having a pH of about 5-8. Compared with the prior art, the invention does not need to undergo complicated chemical modification or cumbersome. The preparation process can be carried out by uniformly mixing the above-mentioned A, B and C to obtain an environmentally-friendly starch adhesive.

Starch in each of the above ingredients: water-soluble polymer: emulsifier: water: cross-linking agent: weight percentage of catalyst (15-40%): (4-10%): (4-10%): (40- 80%): (4-10%): (0.1-0.5%), preferably the weight percentage relationship is (20-30%): (5-8%): (5-8%): (50-70%) ): (5-8%): (0.2-0.3%). Wherein the ratio of component A: component B: component C, the weight percentage relationship is (15-40%): (60-85%): (4-10%), preferably the weight percentage is (20- 30%): (70-80%): (5-8%).

The preparation method of the environmentally-friendly adhesive of the invention comprises the following steps:

(a) Preparation of component B: First, the water-soluble polymer is dissolved in water and placed in a stirred vessel. In order to uniformly dissolve the water-soluble polymer in water, the vessel is heated and heated to control the temperature between about 70 and 90 ° C. 2~3 hours, then the container is cooled at room temperature, and then the emulsifier and the catalyst are sequentially added, wherein the water-soluble polymer: emulsifier: water is about (2-10%) by weight: (2-10) %): (40-80%), preferably (4-8%): (4-8%): (50-70%).

(b) The composition A of the original starch, the component B prepared above, and the component C of the crosslinking agent are the same according to the weight percentage of the component A: component B: component C (15-40%): (60-85%) ): (4-10%), the three components are stirred at room temperature for about 60 minutes to obtain the environmentally friendly starch binder of the present invention.

The environment-friendly starch glue of the invention is mainly applied to wood bonding, such as wooden furniture building materials, fine wood boards and house decoration. In order to apply it to the industry, the environmentally-friendly starch adhesive of the present invention is tested in accordance with the National Standards of the Republic of China CNS 2232 Urea Adhesive Test and the provisions of the CNS 1349 ordinary plywood.

According to the provisions of the CNS 2232 Urea Rubber Test Method, the inspection items are divided into 25 ° C viscosity test, 25 ° C solidification test and 25 ° C, 70 ° C preservation test. The environmentally friendly starch adhesive of the invention has a viscosity of between 2,000 and 3,500 CP at 25 ° C; a solidification test time of about 6 to 8 hours at 25 ° C; a storage test of at least 25 days at 25 ° C, and at least a storage test at 70 ° C It can be more than 20 hours. Therefore, the environmentally friendly starch adhesive of the present invention meets the standards of the CNS 2232 urea gel test method of the Republic of China.

In addition, according to the provisions of the National Standards of the Republic of China on CNS 1349, the glue is glued into the common plywood, and then the ordinary plywood is immersed in water. According to the type of ordinary plywood that can withstand different immersion temperatures and time, it is divided into three grades (CNS Type 1, CNS Type 2, CNS Type 3), and the environmentally friendly starch adhesive of the present invention can reach the level of CNS 1349 Type 1, and the adhesion strength test can reach 30kg/cm ² or more, in line with national standards (10kg/cm ² or more). Regulations.

The environment-friendly starch glue of the invention is mainly composed of three kinds of components, and can be stored at room temperature 25 ° C for at least 30 days, as long as the three components are evenly mixed before use, it is very convenient to use, no It is necessary to go through a complicated temperature rise and fall process and a chemical modification reaction to obtain a glue. Furthermore, the environmentally friendly starch adhesive of the present invention has the following advantages: (1) using native starch as a main raw material, non-petrochemical raw materials, meeting environmental protection requirements and having a low price advantage; (2) the polymer does not contain formaldehyde, no The problem of formaldehyde escape does not endanger human health; (3) The inspection items all meet the CNS national standards, which not only have good adhesiveness and excellent water resistance, but also have better performance than the currently marketed urea-formaldehyde resin, so there is a great future. Potential to become a commercial item.

[Examples] [Example 1] Preparation of component B

60 g of polyethylene glycol and 600 g of water are added to a stirred vessel. In order to uniformly dissolve the polymer in water, the stirred vessel is heated and reacted at a temperature of about 80 to 90 ° C for 2 to 3 hours. The container is placed at room temperature After cooling down, 50 grams of acrylic resin and 2 grams of boric acid are sequentially added to prepare the component B.

[Example 2] Preparation of environmentally friendly starch adhesive

20 g of starch (component A), 75 g of the component B of Example 1 and 5 g of a crosslinking agent were stirred at room temperature for 30 minutes to obtain an environmentally-friendly starch binder of the present invention. 15 g of glue was applied to a wooden board of length × width × height 30 cm × 30 cm × 0.3 mm, another piece of wood of the same specification was covered, and two pieces of wood board were heat-pressed at 150 ° C for 10 minutes, and then it was carried out. test.

[Example 3] Preparation of environmentally friendly starch adhesive

25 g of starch (component A), 70 g of the component B of Example 1 and 5 g of a crosslinking agent were stirred at room temperature for 30 minutes to obtain an environmentally-friendly starch binder of the present invention. 15 grams of glue is applied to the board of length × width × height 30cm × 30cm × 0.3mm, another piece of wood of the same specification is covered, and two pieces of wood board are hot pressed at 130 ° C for 10 minutes, then Carry out inspection.

[Comparative Example] Commercially available adhesive

Take commercially available urea formaldehyde glue, melamine-formaldehyde glue, polyvinyl acetate resin, respectively, 15 grams of the above glue is applied to the board of length × width × height 30cm × 30cm × 0.3mm, the other piece of the same specification Cover the board with a wooden board and heat-press the two boards at 130 ° C for 10 minutes, then test.

[Example 4] Inspection of environmentally friendly starch adhesive

The glues of Examples 2 and 3 were tested according to the method of CNS National Standard CNS 2232 urea glue. The average results of the two are as follows:

It can be known from the experimental results that the environmentally friendly starch adhesive of the present invention has a viscosity of between 2,000 and 3,500 CP at 25 ° C; a solidification test time of about 6 to 8 hours at 25 ° C; and a storage time of up to 30 days at 25 ° C; Above, the storage time at 70 °C can be at least 20 hours, and the above test results are all in line with the CNS 2232 standard.

According to the method of the Chinese National Standard CNS 1349 ordinary plywood, There are three types of inspection methods. As long as the board is subjected to the following procedures, the board is not separated, that is, it meets the standard of this grade.

(1) CNS Type 3 (normal three types): The plate was immersed in water at a temperature of (35 ± 3) ° C for 2 hours, and then dried at a temperature (60 ± 3) ° C for 3 hours.

(2) CNS Type 2 (warm water immersion type 2): The board is immersed in water at a temperature of (70 ± 3) °C for 2 hours, and then dried at a temperature (60 ± 3) °C for 3 hours.

(3) CNS Type 1 (repeated boiled water): After immersing the board in boiling water for 4 hours, continue to dry at temperature (60 ± 3) °C for 20 hours, then immerse in boiling water for 4 hours, at temperature (60 ± 3) °C Dry for 3 hours.

The examples 2 and 3 and the comparative examples were taken for the CNS 1349 ordinary plywood test, and the cementation ability and the formaldehyde escape amount were compared. The comparison results were as follows:

The comparison results show that the glue of the present invention not only has good cementation ability, does not contain toxic substance formaldehyde, and has excellent water resistance, and can reach the standard of CNS Type 1, and therefore, the glue of the present invention has great potential to become a commercial product in the future.

Although the present invention has been disclosed above in several preferred embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art, The scope of protection of the present invention is defined by the scope of the appended claims, unless otherwise claimed.

Claims (13)

The invention relates to a method for preparing an environment-friendly starch glue, comprising: (a) preparing a component B, dissolving a water-soluble polymer in water, and then adding an emulsifier; (b) preparing a component A, the component B obtained above The environment-friendly starch adhesive can be prepared by stirring with a component C at room temperature, wherein the component A comprises an unmodified original starch; the component B comprises the water-soluble polymer, the emulsifier and Water, wherein the emulsifier comprises natural rubber, styrene, vinyl acetate, acrylic resin, polyurethane or epoxy resin; and component C, including the crosslinking agent. The method for preparing an environmentally-friendly starch cement according to claim 1, wherein the component B further comprises a catalyst. The method for preparing an environmentally-friendly starch cement according to claim 2, wherein the catalyst comprises a weak acid solution. The method for preparing an environmentally-friendly starch cement according to claim 3, wherein the weak acid solution comprises citric acid, boric acid, oxalic acid or phosphoric acid. The method for preparing an environmentally-friendly starch cement according to claim 1, wherein the native starch comprises corn starch, potato starch, rice starch, wheat starch or tapioca starch. The method for preparing an environmentally-friendly starch adhesive according to claim 1, wherein the water-soluble polymer comprises a polyhydric alcohol or a polyenamine. The method for preparing an environmentally-friendly starch adhesive according to claim 1, wherein the water-soluble polymer comprises polyethylene glycol (polyethylene) Glycol, PEG), polytetramethylene ether glycol (PTMEG), polyvinyl alcohol (PVA), polyethylene imine or polyallylamine (PAA). The method for preparing an environmentally-friendly starch adhesive according to claim 1, wherein the crosslinking agent comprises melamine, trimethoxy melamine, triethoxy melamine, hexamethoxy Hexamethoxy melamine, hexaethoxy melamine. The method for preparing an environmentally-friendly starch adhesive according to claim 1, wherein the environmentally-friendly starch adhesive has a pH of about 5-8. The method for preparing an environmentally-friendly starch adhesive according to claim 1, wherein the environmentally-friendly starch adhesive does not include formaldehyde. The method for preparing an environmentally-friendly starch adhesive according to claim 1, wherein the environmentally-friendly starch adhesive is applied to wood bonding. For example, the method for preparing an environmentally-friendly starch glue according to claim 1 of the patent scope, wherein the environment-friendly starch glue meets the standards of the CNS National Standards CNS 2232 Urea Rubber Test Method. For example, the method for preparing an environmentally-friendly starch adhesive according to the first aspect of the patent application, wherein the environmentally-friendly starch adhesive meets the CNS Type 1 standard of the CNS 1349 common plywood of the Republic of China.