Environment-friendly EVA modified hot melt adhesive

Abstract

The invention relates to an environment-friendly EVA (Ethylene Vinyl Acetate) modified hot melt adhesive, which is prepared from the following raw materials: EVA resin, an ethylene-acrylic acid-2-ethylhexyl ester polymer, paraffin, rosin and modified starch. The EVA resin accounts for 40 to 60 parts, the ethylene-acrylic acid-2-ethylhexyl ester polymer accounts for 20 to 40 parts, the paraffin accounts for 5 to 15 parts, the rosin accounts for 3 to 10 parts, and the modified starch accounts for 5 to 15 parts based on 100 parts. The modified starch is formed by mixing corn starch, acid, a lubricant and a filler. During preparation, the EVA resin and the ethylene-acrylic acid-2-ethylhexyl ester polymer are firstly blended, and then the mixture, the paraffin, the rosin and the modified starch are mixed and extruded to form the adhesive. The environment-friendly EVA modified hot melt adhesive disclosed by the invention has the advantages of good environmental protection property, optimized performance, reduced cost, wide applicability and the like. Modified starch is adopted to reduce pollution, and no harmful solvent exists; the water resistance, the chemical resistance and the bonding strength are improved; the cost is reduced due to partial replacement of synthetic materials; the method is suitable for various base materials and environments.

Description

Technical Field

[0001] The invention relates to the technical field of wood bonding materials, in particular to an environmentally friendly EVA modified hot melt adhesive. Background Art

[0002] Hot melt adhesive is a plastic adhesive. Its physical state changes with temperature within a certain temperature range, while its chemical properties remain unchanged. It is a non-toxic, tasteless and environmentally friendly chemical product. Due to the characteristics of hot melt adhesive, such as fast bonding speed, no solvent, simple production process, low cost, low equipment investment, convenience and high efficiency, it is widely used in food packaging, fast assembly line packaging and sealing, home appliance sealing, book binding, floor gluing and other industries. Existing building decoration floor materials are becoming more and more high-end and beautiful, and the floor materials at home are mostly made of wood. When manufacturing the floor material, especially for multi-layer boards, the environmental protection of the gluing used is particularly concerned, because for daily use of adhesives, whether it is harmful to the human body is very critical.

[0003] In the current hot melt adhesive field, EVA hot melt adhesive is widely used due to its wide source of raw materials, low cost and high bonding strength. Although EVA hot melt adhesive has so many advantages, it still has the following defects, such as environmental pollution, health risks, and poor water resistance and drug resistance of existing adhesives, which limits the use of floor materials in humid environments. Summary of the invention

[0004] In view of this, the present invention provides an environmentally friendly EVA modified hot melt adhesive to solve the above technical problems.

[0005] An environmentally friendly EVA modified hot melt adhesive, the raw materials for its preparation are composed of EVA resin, ethylene-2-ethylhexyl acrylate polymer, paraffin wax, rosin, and modified starch. Based on 100 points, the EVA resin accounts for 40 to 60 parts, the ethylene-2-ethylhexyl acrylate polymer accounts for 20 to 40 parts, the paraffin wax accounts for 5 to 15 parts, the rosin accounts for 3 to 10 parts, and the modified starch accounts for 5 to 15 parts. The modified starch is mixed with corn starch, acid, lubricant and filler. During the preparation, the EVA resin is first blended with the ethylene-2-ethylhexyl acrylate polymer, and then mixed with the paraffin wax, rosin, and modified starch for extrusion.

[0006] Furthermore, the mass fraction of acrylic acid in the ethylene-2-ethylhexyl acrylic acid ester polymer copolymer is 0.1% to 35.0%.

[0007] Furthermore, the EVA resin accounts for 45, 50, or 55 parts.

[0008] Furthermore, the ethylene-2-ethylhexyl acrylate polymer accounts for 20, 25, or 30 parts.

[0009] Furthermore, based on 100 parts of the modified starch, the content of the corn starch is 50 to 70 parts, the content of the acid is 1 to 5 parts, the content of the lubricant is 1 to 3 parts, and the content of the filler is 10 to 30 parts.

[0010] Furthermore, the acid may be one of citric acid, tartaric acid and hydrochloric acid.

[0011] Furthermore, the lubricant may be one of stearic acid, polyethylene wax and paraffin.

[0012] Furthermore, the filler may specifically be one of calcium carbonate, talc and silicon dioxide.

[0013] Furthermore, the paraffin accounts for 8, 10, or 12 parts.

[0014] Furthermore, the rosin accounts for 5, 7, or 8 parts.

[0015] Compared with the prior art, the environmentally friendly EVA modified hot melt adhesive of the present invention selects the ethylene-2-ethylhexyl acrylate polymer and the EVA resin for first blending, so that the formed mixture has stronger intermolecular forces, and then the hot melt adhesive has stronger stability, so that the water resistance, chemical resistance and bonding strength of the modified hot melt adhesive are improved. By using paraffin and rosin, the melt index, gluing temperature and adhesion can be adjusted, so that the hot melt adhesive is suitable for a variety of substrates and environments. The use of modified starch can reduce pollution, and the cost is reduced by partially replacing synthetic materials. Therefore, the EVA hot melt adhesive has the advantages of good environmental protection, optimized performance, reduced cost, and wide applicability. DETAILED DESCRIPTION

[0016] The specific embodiments of the present invention are further described in detail below. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the protection scope of the present invention.

[0019] The present invention provides an environmentally friendly EVA modified hot melt adhesive, which includes EVA resin, ethylene-2-ethylhexyl acrylate polymer, paraffin wax, rosin, and modified starch. Based on 100 points, the EVA resin accounts for 40 to 60 parts, the ethylene-2-ethylhexyl acrylate polymer accounts for 20 to 40 parts, the paraffin wax accounts for 5 to 15 parts, the rosin accounts for 3 to 10 parts, and the modified starch accounts for 5 to 15 parts.

[0020] The EVA resin, namely ethylene-vinyl acetate copolymer (EVA for short), is a general-purpose high molecular polymer with a molecular formula of (C2H4)x.(C4H6O2)y. It is flammable and has a non-irritating burning smell. EVA has good low-temperature resistance and a low thermal decomposition temperature of about 230°C. As the molecular weight increases, the softening point of EVA rises, the processability and the glossiness of the surface of the plastic part decrease, but the strength increases, and the impact toughness and environmental stress cracking resistance are improved. In the invention, the EVA resin accounts for 40 to 60 parts. If it is less than 40 parts, the strength of the hot melt adhesive will be insufficient, and the impact toughness and environmental stress cracking resistance will be reduced. Since the EVA resin plays an important basic role in the formula, insufficient content will reduce the overall performance of the hot melt adhesive and fail to meet the requirements of applications such as floor gluing. If the content of the EVA resin is higher than 60 parts, the softening point will increase and the workability will decrease, which will make the hot melt adhesive more difficult to operate during the construction process, such as causing glue overflow, thereby affecting the appearance quality of the final product.

[0021] The ethylene-2-ethylhexyl acrylate polymer is prepared by copolymerizing ethylene and acrylic acid under high pressure through a free radical mechanism. Its production process is similar to the production process of high-pressure polyethylene, that is, ethylene, acrylic acid, and a peroxide initiator are added into a high-pressure reactor, and copolymerization is carried out under the conditions of a temperature of 100 to 250° C. and a pressure of 108 MPa to 186 MPa to obtain the ethylene-2-ethylhexyl acrylate polymer copolymer with an acrylic acid mass fraction of 0.1% to 35.0%.

[0022] The ethylene-2-ethylhexyl acrylic acid is used to improve the thermal stability of the EVA resin, so that it can maintain stable performance under high-temperature use environment, thereby extending the life of the hot melt adhesive, and then extending the life of the board using the hot melt adhesive, and avoiding its debonding. At the same time, the ethylene-2-ethylhexyl acrylic acid also has good bonding properties, so that the initial adhesion and lasting adhesion of the hot melt adhesive can be enhanced, and the bonding effect of the adhesive on various substrates can be improved. The content of the ethylene-2-ethylhexyl acrylic acid must be controlled at 20 to 40 parts. If it is less than 20 parts, it will not be able to fully exert its role in improving adhesion and flexibility, resulting in insufficient bonding between the hot melt adhesive and the substrate, and easy debonding and other problems. If it is higher than 40 parts, the hardness of the hot melt adhesive will increase and the flexibility will decrease, affecting its impact resistance during use.

[0023] When making the hot melt adhesive, the EVA resin and the ethylene-2-ethylhexyl acrylate are first blended. The purpose of blending is to improve the performance of the hot melt adhesive. Mixing the two polymers first can promote the intermolecular interaction forces between them, such as van der Waals forces and hydrogen bonds. These interactions help to form a more stable structure and improve the overall stability of the hot melt adhesive. Through blending, the advantages of the two polymers can be fully utilized, and the performance indicators such as the softening point, melt index, adhesion, and flexibility of the hot melt adhesive can be adjusted to make it more suitable for applications such as floor gluing. At the same time, the stability of the hot melt adhesive can also be improved by blending, that is, the two polymers can interact with each other by blending to form a more stable structure, and the heat resistance, water resistance and chemical resistance of the hot melt adhesive can be improved. If not blended, or if the EVA resin and the ethylene-2-ethylhexyl acrylate are not first blended, the advantages of the two polymers cannot be fully utilized, and the performance of the hot melt adhesive may not meet the requirements of applications such as floor gluing, and the performance stability of the hot melt adhesive cannot be guaranteed, so that problems such as delamination and cracking are prone to occur. Because if the EVA resin is blended with the ethylene-2-ethylhexyl acrylate, if there are other substances involved, such as paraffin or rosin, they will block the intermolecular interaction between the two polymers during blending, which is not conducive to the two polymers complementing each other to form a stable intermolecular structure, thereby improving the stability of the hot melt adhesive. This is also an important reason for selecting the ethylene-2-ethylhexyl acrylate in this embodiment.

[0024] The paraffin wax is a hydrocarbon mixture extracted from certain distillates of petroleum, shale oil or other asphalt mineral oils. The paraffin wax is used to adjust the melting index and gluing temperature of the EVA modified hot melt adhesive. Since the sheet needs to be fully bonded and interpenetrated with the hot melt adhesive when gluing, it is necessary to make the hot melt adhesive reach a certain temperature. The paraffin wax can not only make the hot melt adhesive better adapt to the surface shape of the floor after heating, improve the uniformity of coating and bonding strength, but also reduce energy consumption during construction, that is, reduce the melting temperature of the hot melt adhesive, thereby reducing the risk of thermal damage to substrates such as floors. The content of the paraffin wax should be controlled between 5 and 15 parts. If the content is less than 5 parts, it will not be able to fully play the role of adjusting the melting index and gluing temperature, resulting in insufficient fluidity of the hot melt adhesive and too high gluing temperature, affecting construction efficiency and quality. If the content is higher than 15 parts, the hardness of the hot melt adhesive will be reduced, the bonding strength will be reduced, and degumming and other problems will easily occur.

[0025] The rosin is a kind of oil tree rosin in the pine family, and its main component is C19H29COOH, which is mainly used to adjust the melt index and gluing temperature of the hot melt adhesive. However, the rosin is also used to improve the adhesion and water resistance of the hot melt adhesive, and can also adjust the softening point and fluidity of the hot melt adhesive. After the rosin resin is added to the hot melt adhesive, the carboxyl group in the rosin resin interacts with the carboxyl group of the EVA resin, thereby destroying the original crystalline structure, thereby greatly improving the fluidity of the hot melt adhesive. At the same time, the rosin can also improve the wetting performance and bonding ability of the hot melt adhesive. The use of the rosin and the paraffin together can enable the hot melt adhesive to maintain good performance under different temperature and humidity conditions. The content of the rosin should be controlled between 3 and 10 parts. If the content is less than 3 parts, it will lead to the inability to give full play to the role of the rosin in adjusting the melt index and gluing temperature, as well as improving the adhesion and water resistance. If the content is higher than 10 parts, the hardness of the hot melt adhesive increases and the flexibility decreases, affecting its impact resistance during use.

[0026] The modified starch is mixed with corn starch, acid, lubricant and filler. The main function of the modified starch is to reduce costs. Since the modified starch is a natural polymer material with a relatively low price, it can partially replace synthetic materials such as EVA resin and reduce the cost of hot melt adhesive. In addition, the modified starch can also improve the environmental performance of the hot melt adhesive, because the modified starch is a biodegradable material, and the use of modified starch can reduce the pollution of the hot melt adhesive to the environment. At the same time, the modified starch can also improve the performance of the hot melt adhesive, such as adjusting the melt index, gluing temperature, adhesion and other performance indicators of the hot melt adhesive, making it more suitable for applications such as floor gluing. The corn starch is modified by the acid, so that the corn starch can undergo a hydrolysis reaction, reduce its molecular weight, and improve its solubility and fluidity. At the same time, the acid can also adjust the pH value of the modified starch, making it more suitable for mixing with other ingredients. The acid can be one of citric acid, tartaric acid and hydrochloric acid. The corn starch is modified by the lubricant, which can reduce the friction between the modified corn starch and other ingredients and improve the processing performance of the hot melt adhesive. At the same time, the lubricant can also improve the surface gloss and demoulding performance of the hot melt adhesive. The lubricant can be one of stearic acid, polyethylene wax, and paraffin. The filler is used to increase the strength and hardness of the modified corn starch and improve the heat resistance and water resistance of the hot melt adhesive. At the same time, the filler can also reduce the cost of the hot melt adhesive. The filler can specifically be one of calcium carbonate, talcum powder, and silicon dioxide.

[0027] When the corn starch is modified, the corn starch is the main component of the modified starch. Taking the modified starch powder as 100 parts, the content of the corn starch is generally above 50 to 70 parts. Less than 50 parts will cause the performance of the modified starch to decline and fail to meet the requirements of the hot melt adhesive. More than 70 parts will increase the cost of the modified starch. The content of the acid is generally between 1 and 5 parts. Less than 1 part will not fully exert the hydrolysis of the acid, affecting the performance of the modified starch. More than 5 parts will cause excessive hydrolysis of the starch, reducing the strength and stability of the modified starch. The content of the lubricant is generally between 1 and 3 parts. Less than 1 part cannot fully exert the role of the lubricant, affecting the processing performance of the hot melt adhesive. More than 3 parts will make the surface of the hot melt adhesive too smooth, affecting its bonding with the substrate. The content of the filler is generally between 10 and 30 parts. Less than 10 parts cannot fully exert the reinforcing effect of the filler, affecting the performance of the hot melt adhesive. If the content is higher than 30 parts, the hardness of the hot melt adhesive will increase, and its flexibility will decrease, thus affecting its impact resistance during use.

[0028] The content of the modified starch should be controlled between 5 and 15 parts. If the content is less than 5 parts, it will not be able to fully play its role in reducing costs, improving environmental performance and improving the performance of the hot melt adhesive. If the content is higher than 15 parts, the hardness of the hot melt adhesive will increase, the flexibility will decrease, and its impact resistance will be affected during use.

[0029] When making the hot melt adhesive, the EVA resin and the ethylene-2-ethylhexyl acrylate are first blended, and then the blended mixture is mixed with the paraffin, rosin, and modified starch and extruded.

[0030] Embodiment 1

[0031] EVA resin: 45 parts; ethylene-2-ethylhexyl acrylate polymer: 25 parts; paraffin wax: 8 parts; rosin: 5 parts; modified starch: 8 parts (based on 100 parts, corn starch: 70 parts, citric acid: 3 parts, stearic acid: 1.5 parts, calcium carbonate: 15.5 parts)

[0032] Embodiment 2

[0033] EVA resin: 50 parts; ethylene-2-ethylhexyl acrylate polymer: 30 parts; paraffin wax: 10 parts; rosin: 7 parts; modified starch: 10 parts (based on 100 parts, corn starch: 65 parts, tartaric acid: 4 parts, polyethylene wax: 2 parts, talc: 29 parts)

[0034] Embodiment 3

[0035] EVA resin: 55 parts; ethylene-2-ethylhexyl acrylate polymer: 35 parts; paraffin wax: 12 parts; rosin: 8 parts; modified starch: 12 parts (based on 100 parts, corn starch: 60 parts, hydrochloric acid: 4.5 parts, paraffin wax: 1.5 parts, silicon dioxide: 34 parts)

[0036] Comparative Example

[0037] The comparative example uses a polyurethane adhesive commonly used in the prior art.

[0038] Table 1

[0039]

[0040]

[0041] From the above comparison, it can be seen that the hot melt adhesive provided by the invention is much stronger than the existing commonly used adhesive polyurethane adhesive in terms of water resistance and chemical resistance. Moreover, the hot melt adhesive has very good dipping and peeling performance. After dipping for 48 hours, there is still no peeling phenomenon, while the commonly used polyurethane adhesive has peeling phenomenon. The 48-hour dipping has greatly exceeded the soaking time of liquid substances on the board under normal circumstances.

[0042] Compared with the prior art, the environmentally friendly EVA modified hot melt adhesive of the present invention selects the ethylene-2-ethylhexyl acrylate polymer and the EVA resin for first blending, so that the formed mixture has stronger intermolecular forces, and then the hot melt adhesive has stronger stability, so that the water resistance, chemical resistance and bonding strength of the modified hot melt adhesive are improved. By using paraffin and rosin, the melt index, gluing temperature and adhesion can be adjusted, so that the hot melt adhesive is suitable for a variety of substrates and environments. The use of modified starch can reduce pollution, and the cost is reduced by partially replacing synthetic materials. Therefore, the EVA hot melt adhesive has the advantages of good environmental protection, optimized performance, reduced cost, and wide applicability.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution or improvement within the spirit of the present invention is included in the scope of the claims of the present invention.

Claims

1. An environmentally friendly EVA modified hot melt adhesive, characterized in that: The raw materials for preparing the environmentally friendly EVA modified hot melt adhesive are composed of EVA resin, ethylene-2-ethylhexyl acrylate polymer, paraffin wax, rosin, and modified starch. Based on 100 points, the EVA resin accounts for 40 to 60 parts, the ethylene-2-ethylhexyl acrylate polymer accounts for 20 to 40 parts, the paraffin wax accounts for 5 to 15 parts, the rosin accounts for 3 to 10 parts, and the modified starch accounts for 5 to 15 parts. The modified starch is mixed with corn starch, acid, lubricant and filler. During preparation, the EVA resin is first blended with the ethylene-2-ethylhexyl acrylate polymer, and then mixed with the paraffin wax, rosin and modified starch by extrusion.

2. The environmentally friendly EVA modified hot melt adhesive according to claim 1, characterized in that: The mass fraction of acrylic acid in the ethylene-2-ethylhexyl acrylic acid copolymer is 0.1% to 35.0%.

3. The environmentally friendly EVA modified hot melt adhesive according to claim 1, characterized in that: The EVA resin accounts for 45, 50, or 55 parts.

4. The environmentally friendly EVA modified hot melt adhesive according to claim 1, characterized in that: The ethylene-2-ethylhexyl acrylate polymer accounts for 20, 25, or 30 parts.

5. The environmentally friendly EVA modified hot melt adhesive according to claim 1, characterized in that: Based on 100 parts of the modified starch, the content of the corn starch is 50 to 70 parts, the content of the acid is 1 to 5 parts, the content of the lubricant is 1 to 3 parts, and the content of the filler is 10 to 30 parts.

6. The environmentally friendly EVA modified hot melt adhesive according to claim 5, characterized in that: The acid can be one of citric acid, tartaric acid and hydrochloric acid.

7. The environmentally friendly EVA modified hot melt adhesive according to claim 5, characterized in that: The lubricant can be one of stearic acid, polyethylene wax and paraffin.

8. The environmentally friendly EVA modified hot melt adhesive according to claim 5, characterized in that: The filler may specifically be one of calcium carbonate, talc and silicon dioxide.

9. The environmentally friendly EVA modified hot melt adhesive according to claim 1, characterized in that: The paraffin wax accounts for 8, 10, or 12 parts.

10. The environmentally friendly EVA modified hot melt adhesive according to claim 1, characterized in that: The rosin accounts for 5, 7, or 8 parts.

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