Hot melt adhesive for lost foam as well as preparation method and application of hot melt adhesive

Abstract

The invention belongs to the technical field of hot melt adhesives, and particularly discloses a hot melt adhesive for an evanescent mode and a preparation method and application of the hot melt adhesive, and the hot melt adhesive comprises the following raw material components in parts by weight: 5-10 parts of a viscosity modifier, 35-45 parts of an ethylene-vinyl acetate copolymer, 5-10 parts of a hydrophilic agent, 40-50 parts of tackifying resin, 0.05-0.1 part of toner and 0.1-1.0 part of an antioxidant. The hydrophilic agent mainly plays a role in improving the hydrophilic performance of the hot melt adhesive, so that when the fireproof coating is brushed at the bonding position of the evanescent mode, the fireproof coating can be uniformly, flatly and effectively attached to the hot melt adhesive, flaws are prevented from being generated on a subsequently cast metal casting, and meanwhile, the high-temperature resistance of the hot melt adhesive can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of hot melt adhesives, and in particular to a hot melt adhesive for lost foam and a preparation method and application thereof. Background Art

[0002] Lost foam casting is a solid casting technology that uses a foam plastic mold (usually expandable polystyrene) with binder-free dry sand combined with vacuum technology. The principle is to bond foam models with similar size and shape to the casting into a model cluster, brush refractory coating and dry it, bury it in dry quartz sand for vibration molding, pour it under negative pressure, gasify the model, and the liquid metal occupies the model position. After solidification and cooling, it forms a new casting method for castings.

[0003] The lost foam, that is, the foam model, needs to be bonded with adhesive or tape before the refractory coating is applied. The split model needs to be bonded together to form a model cluster before the refractory coating can be applied to the whole model. Due to the reasons that traditional adhesives (water-based adhesives, solvent-based adhesives) and tapes are not environmentally friendly, have a strong odor, dry slowly, and are inconvenient to apply, they are gradually being replaced by hot melt adhesives.

[0004] Hot melt adhesive is environmentally friendly, odorless, has high bonding strength, can be applied continuously and conveniently, dries quickly after application and can immediately form bonding strength, has a suitable flash point (200-300℃), and after pouring liquid metal (1500-1600℃), the foam model and hot melt adhesive burn to form carbon dioxide and water, and there are no other impurities that affect the appearance of the casting. However, traditional hot melt adhesives are generally hydrophobic, and when the refractory coating is applied on the hot melt adhesive surface at the bonding point of the lost foam, small water droplets will form on the hot melt adhesive, causing the refractory coating to not adhere evenly to the hot melt adhesive surface, affecting the refractory coating application effect, and causing defects on the surface of the metal casting. Summary of the invention

[0005] In order to overcome the defects of the prior art, the present invention provides a hot melt adhesive for lost foam and a preparation method and application thereof.

[0006] The technical solution adopted by the present invention to solve its technical problem is: The first scheme of the present invention provides a hot melt adhesive for lost foam, wherein the raw materials of the hot melt adhesive include the following components in weight percentage: 5 to 10 parts of viscosity regulator, 35 to 45 parts of ethylene-vinyl acetate copolymer, 5 to 10 parts of hydrophilic agent, 40 to 50 parts of tackifying resin, 0.05 to 0.1 parts of color powder and 0.1 to 1.0 parts of antioxidant.

[0007] The idea of ​​solving the problem of the present invention is that the hydrophilic agent mainly plays the role of increasing the hydrophilicity of the hot melt adhesive, so that when the refractory coating is brushed on the bonding part of the lost foam, the refractory coating can be evenly, smoothly and effectively attached to the hot melt adhesive, thereby avoiding defects on the subsequently cast metal castings, and at the same time improving the high temperature resistance of the hot melt adhesive.

[0008] As a further solution, the hydrophilic agent is BASF HL560. BASF HL560 has good hydrophilicity and high temperature resistance.

[0009] As a further solution, the ethylene-vinyl acetate copolymer consists of a component A with a VA content of 31-33% and a component B with a VA content of 18-20%, and the weight ratio of the component A to the component B is 2-4:1.

[0010] Specifically, ethylene-vinyl acetate copolymer mainly plays a bonding role, increasing the bonding strength of the hot melt adhesive to the lost foam and improving the adhesion of the refractory coating on the surface of the hot melt adhesive. In addition, the higher the VA content in the ethylene-vinyl acetate copolymer, the better the hydrophilicity, but the weaker the cohesive strength and the worse the high-temperature bonding performance; while the lower the VA content in the ethylene-vinyl acetate copolymer, the worse the hydrophilicity, but the better the high-temperature bonding performance. Therefore, by compounding two ethylene-vinyl acetate copolymers with different VA contents, the hot melt adhesive can achieve good hydrophilicity and high-temperature bonding performance at the same time.

[0011] As a further solution, the viscosity modifier is at least one of Sinopec 58# fully refined paraffin wax and Sinopec 80# microcrystalline wax. Specifically, the viscosity modifier mainly plays the role of reducing viscosity, increasing the permeability of the hot melt adhesive to the lost foam, and improving the quick-drying performance of the hot melt adhesive.

[0012] As a further solution, the tackifying resin is at least one of Komao rosin resin 146 and Komao KA120. Specifically, the tackifying resin mainly plays the role of increasing viscosity, improving the adhesion of the refractory coating on the surface of the hot melt adhesive, and improving cohesion and high temperature resistance.

[0013] As a further solution, the color powder is Meize M169. The color powder can be used to adjust the color of the hot melt adhesive, thereby increasing the recognition of the hot melt adhesive when it is used.

[0014] As a further solution, the antioxidant is at least one of Lianlong 1010 and Lianlong 168. The antioxidant mainly plays a role in reducing the problem of oxidation of the above materials when heated at high temperature and used at room temperature.

[0015] The second solution of the present invention is to provide a method for preparing a hot melt adhesive for lost foam, the method for preparing the above-mentioned hot melt adhesive for lost foam, the method for preparing comprises the following steps: 1) Add viscosity regulator and antioxidant to a reaction kettle heated to 90-110°C, stir at a stirring speed of 45-55 rpm, and continue heating to 120-140°C; 2) After all materials in the reactor are melted into liquid, add all the ethylene-vinyl acetate copolymer, stir at a stirring speed of 45-55 rpm, maintain the temperature at 120-140°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add tackifying resin, color powder and hydrophilic agent, stir at a stirring speed of 45-55 rpm, maintain the temperature at 100-110°C, and continue to evacuate to -0.08 MPa. After all materials are melted evenly, the above-mentioned hot melt adhesive is obtained.

[0016] Specifically, in step 1) of the above preparation method, the viscosity modifier and the antioxidant are first heated and stirred, the purpose is to make the viscosity modifier melt first and then have a low viscosity, which is conducive to reducing the overall viscosity of the material in the process of melting the ethylene-vinyl acetate copolymer in step 2), so that the ethylene-vinyl acetate copolymer melts more evenly, and the operator can make a better judgment (the above reaction is carried out in a reactor, and the stirring paddle is driven by a motor for stirring, so the viscosity of the hot melt adhesive needs to be low to avoid damaging the motor). At the same time, the antioxidant can also reduce the oxidation and chemical bond breaking of the material during the entire high-temperature heating reaction process, ensuring the stability of the material. In step 3), the tackifying resin and the hydrophilic agent are added together at the end, which is also convenient for controlling the discharge temperature of the final product and facilitating the discharge (the hot melt adhesive of the present invention can be granular. If the discharge temperature is high, the hot melt adhesive needs to cool for a longer time, and the granular hot melt adhesive is easy to stick into blocks).

[0017] The third solution of the present invention is to provide the application of the above-mentioned hot melt adhesive in lost foam casting.

[0018] The present invention has at least one of the following beneficial effects:.

[0019] 1. The hydrophilic agent mainly plays the role of increasing the hydrophilicity of the hot melt adhesive, so that when the refractory coating is brushed on the bonding part of the lost foam, the refractory coating can be evenly, smoothly and effectively attached to the hot melt adhesive, thereby avoiding defects on the subsequent metal castings and improving the high temperature resistance of the hot melt adhesive.

[0020] 2. By compounding two ethylene-vinyl acetate copolymers with different VA contents, the hot melt adhesive can achieve good hydrophilicity and high-temperature bonding properties at the same time.

[0021] 3. When bonding the lost foam of foam material, the curing time is short and the hot melt adhesive cools down quickly, which will not damage or deform the lost foam. It ensures that the coating layer is flat when the refractory coating is applied on the surface of the lost foam bonding part, and the surface of the final metal casting is flat without defects.

[0022] 4. The hot melt adhesive of the present invention dries quickly after bonding, has a short curing time, and can quickly form a lost foam with fixed bonding strength. DETAILED DESCRIPTION

[0023] It should be noted that the following descriptions of the embodiments are used to help understand the present invention, but do not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] It should be noted that both component A and component B are ethylene-vinyl acetate copolymers, and the only difference is the VA content. The hot melt adhesives formed in the following embodiments can all be applied to lost foam casting.

[0025] Example 1 This embodiment provides a hot melt adhesive for lost foam, the raw materials of the hot melt adhesive include the following components in parts by weight: 5 parts of viscosity modifier, 35 parts of ethylene-vinyl acetate copolymer, 5 parts of hydrophilic agent, 50 parts of tackifying resin, 0.05 parts of color powder and 0.6 parts of antioxidant; The ethylene-vinyl acetate copolymer consists of a component A with a VA content of 30% and a component B with a VA content of 19%, and the weight ratio of the component A to the component B is 3:1.

[0026] The preparation method of the hot melt adhesive comprises the following steps: 1) Add 5 parts of viscosity modifier and 0.6 parts of antioxidant to a reactor heated to 100°C, stir at a stirring speed of 50 rpm, and continue heating to 130°C; the viscosity modifier is Sinopec 58# fully refined paraffin, and the antioxidant is Lianlong 1010; 2) After all materials in the reactor are melted into liquid, add 35 parts of ethylene-vinyl acetate copolymer, stir at a stirring speed of 50 rpm, maintain the temperature at 130°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add 50 parts of tackifying resin, 0.05 parts of color powder and 5 parts of hydrophilic agent, stir at a stirring speed of 50 rpm, maintain the temperature at 105°C, and continue to evacuate to -0.08 MPa. After all materials are melted evenly, the above-mentioned hot melt adhesive is obtained, wherein the tackifying resin is Komao rosin resin 146, the color powder is Mezer M169, and the hydrophilic agent is BASF HL560.

[0027] Example 2 This embodiment provides a hot melt adhesive for lost foam, the raw materials of the hot melt adhesive include the following components in parts by weight: 10 parts of viscosity modifier, 40 parts of ethylene-vinyl acetate copolymer, 8 parts of hydrophilic agent, 40 parts of tackifying resin, 0.75 parts of color powder and 0.1 parts of antioxidant; The ethylene-vinyl acetate copolymer consists of a component A with a VA content of 31% and a component B with a VA content of 18%, and the weight ratio of the component A to the component B is 3:1.

[0028] The preparation method of the hot melt adhesive comprises the following steps: 1) Add 10 parts of viscosity modifier and 0.1 parts of antioxidant to a reactor heated to 100°C, stir at a stirring speed of 50 rpm, and continue heating to 130°C; the viscosity modifier is Sinopec 80# microcrystalline wax, and the antioxidant is Lianlong 168; 2) After all materials in the reactor are melted into liquid, add all the ethylene-vinyl acetate copolymer, stir at a stirring speed of 50 rpm, maintain the temperature at 130°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add 40 parts of tackifying resin, 0.75 parts of color powder and 8 parts of hydrophilic agent, stir at a stirring speed of 50 rpm, keep the temperature at 105°C, and continue to evacuate to -0.08mpa. After all materials are melted evenly, the above hot melt adhesive is obtained. Among them, the tackifying resin is Kemao KA120, the color powder is Meize M169, and the hydrophilic agent is BASF HL560.

[0029] Example 3 This embodiment provides a hot melt adhesive for lost foam, the raw materials of the hot melt adhesive include the following components in parts by weight: 8 parts of viscosity modifier, 45 parts of ethylene-vinyl acetate copolymer, 10 parts of hydrophilic agent, 45 parts of tackifying resin, 0.1 parts of color powder and 1 part of antioxidant; The ethylene-vinyl acetate copolymer consists of a component A with a VA content of 33% and a component B with a VA content of 20%, and the weight ratio of the component A to the component B is 3:1.

[0030] The preparation method of the hot melt adhesive comprises the following steps: 1) Add 8 parts of viscosity modifier and 1 part of antioxidant to a reactor heated to 100°C, stir at a stirring speed of 50 rpm, and continue heating to 130°C; the viscosity modifier is Sinopec 80# microcrystalline wax, and the antioxidant is Lianlong 168; 2) After all materials in the reactor are melted into liquid, add all the ethylene-vinyl acetate copolymer, stir at a stirring speed of 50 rpm, maintain the temperature at 130°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add 45 parts of tackifying resin, 0.1 parts of color powder and 10 parts of hydrophilic agent, stir at a stirring speed of 50 rpm, keep the temperature at 105°C, and continue to evacuate to -0.08mpa. After all materials are melted evenly, the above hot melt adhesive is obtained. Among them, the tackifying resin is Kemao KA120, the color powder is Meize M169, and the hydrophilic agent is BASF HL560.

[0031] Example 4 This embodiment provides a hot melt adhesive for lost foam, the raw materials of the hot melt adhesive include the following components in parts by weight: 8 parts of viscosity modifier, 45 parts of ethylene-vinyl acetate copolymer, 10 parts of hydrophilic agent, 45 parts of tackifying resin, 0.1 parts of color powder and 1 part of antioxidant; The ethylene-vinyl acetate copolymer consists of a component A with a VA content of 33% and a component B with a VA content of 20%, and the weight ratio of the component A to the component B is 2:1.

[0032] The preparation method of the hot melt adhesive comprises the following steps: 1) Add 8 parts of viscosity modifier and 1 part of antioxidant to a reactor heated to 100°C, stir at a stirring speed of 50 rpm, and continue heating to 130°C; the viscosity modifier is Sinopec 80# microcrystalline wax, and the antioxidant is Lianlong 168; 2) After all materials in the reactor are melted into liquid, add all the ethylene-vinyl acetate copolymer, stir at a stirring speed of 50 rpm, maintain the temperature at 130°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add 45 parts of tackifying resin, 0.1 parts of color powder and 10 parts of hydrophilic agent, stir at a stirring speed of 50 rpm, keep the temperature at 105°C, and continue to evacuate to -0.08mpa. After all materials are melted evenly, the above hot melt adhesive is obtained. Among them, the tackifying resin is Kemao KA120, the color powder is Meize M169, and the hydrophilic agent is BASF HL560.

[0033] Example 5 This embodiment provides a hot melt adhesive for lost foam, the raw materials of the hot melt adhesive include the following components in parts by weight: 8 parts of viscosity modifier, 45 parts of ethylene-vinyl acetate copolymer, 10 parts of hydrophilic agent, 45 parts of tackifying resin, 0.1 parts of color powder and 1 part of antioxidant; The ethylene-vinyl acetate copolymer consists of a component A with a VA content of 33% and a component B with a VA content of 20%, and the weight ratio of the component A to the component B is 4:1.

[0034] The preparation method of the hot melt adhesive comprises the following steps: 1) Add 8 parts of viscosity modifier and 1 part of antioxidant to a reactor heated to 100°C, stir at a stirring speed of 50 rpm, and continue heating to 130°C; the viscosity modifier is Sinopec 80# microcrystalline wax, and the antioxidant is Lianlong 168; 2) After all materials in the reactor are melted into liquid, add all the ethylene-vinyl acetate copolymer, stir at a stirring speed of 50 rpm, maintain the temperature at 130°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add 45 parts of tackifying resin, 0.1 parts of color powder and 10 parts of hydrophilic agent, stir at a stirring speed of 50 rpm, keep the temperature at 105°C, and continue to evacuate to -0.08mpa. After all materials are melted evenly, the above hot melt adhesive is obtained. Among them, the tackifying resin is Kemao KA120, the color powder is Meize M169, and the hydrophilic agent is BASF HL560.

[0035] Comparative Example 1 The difference from Example 1 is that no hydrophilic agent is added to the raw material components of the hot melt adhesive, and the other components and preparation method are consistent with those of Example 1.

[0036] Comparative Example 2 The difference from Example 1 is that the ethylene-vinyl acetate copolymer is all component A with a VA content of 33%, and the other components and preparation method are consistent with those of Example 1.

[0037] Comparative Example 3 The difference from Example 1 is that the ethylene-vinyl acetate copolymer is all B component with a VA content of 20%, and the other components and preparation method are consistent with Example 1.

[0038] Performance Testing The hot melt adhesives prepared in the above Examples 1-5 and Comparative Examples 1-3 were subjected to relevant performance tests, and the test items, methods and results are shown in the following table: ①Viscosity detection method: The viscosity was tested with reference to method A in HG / T3660-1999, the recommended standard for the chemical industry. The test temperature was 160°C. The viscosity was tested using a DV2T viscometer and a No. 27 rotor from Brookfield, USA. The results were expressed in centipoise (cps).

[0039] ② Softening point detection method: The test was carried out according to the method in GB / T15330-1994 and the results were expressed in (℃).

[0040] ③ Detection method of curing time: Put 20 grams of hot melt adhesive sample into the heating barrel of the glue sprayer, set the temperature to 140℃ and heat and melt for 15 minutes, control the spraying length to 20cm and the weight of 1g of hot melt adhesive on the foam board, press another foam board with the hot melt adhesive and start timing. The shortest time that can cause damage when tearing the foam board is the curing time, and the result is expressed in (seconds).

[0041] ④Test method for bonding at room temperature: The hot melt adhesive sample was placed in an oven and heated to 140°C, evenly coated on two lost foams, pressed and cooled, and left at room temperature for 24 hours before tearing open the foam board to observe the damage effect.

[0042] ⑤High temperature bonding detection method: The hot melt adhesive sample was placed in an oven and heated to 140°C, evenly coated on two lost foams for pressing and cooling, left at room temperature for 24 hours, and then placed in an oven at 45°C for 4 hours. The foam board was torn open to observe the damage effect.

[0043] ⑥ Hydrophilicity testing method: Cut the hot melt adhesive sample into a 10cm*2cm*1cm cuboid, put it into the prepared refractory coating, soak it for 5 seconds and then take it out to observe whether the refractory coating is evenly attached to the hot melt adhesive sample.

[0044] The test results are shown in Table 1 below: Combining Example 1 and Comparative Example 1, it can be seen that the coating in Example 1 adheres evenly, indicating that the hot melt adhesive has good hydrophilicity; the coating in Comparative Example 1 adheres unevenly in the form of small water droplets, indicating that the hot melt adhesive has poor hydrophilicity, further illustrating that the present invention significantly improves the hydrophilicity of the hot melt adhesive, and the refractory coating can form a uniform, smooth and effective coating layer on the surface after being brushed on the hot melt adhesive at the bonding point of the lost foam to protect the metal casting and avoid defects in the metal casting.

[0045] Combining Example 1, Comparative Example 2 and Comparative Example 3, it can be seen that the coating of Comparative Example 2 is uniformly attached, and the 20% damage value is low, indicating that the hot melt adhesive has good hydrophilicity, but poor high-temperature bonding performance; the coating of Comparative Example 3 is unevenly attached, in the form of small water droplets, and the 100% damage value is high, indicating that the hot melt adhesive has poor hydrophilicity, but good high-temperature bonding performance. It further illustrates that the compounding of two ethylene-vinyl acetate copolymers with different VA contents has improved hydrophilicity and high-temperature bonding performance compared to component A or component B with only a single VA content, indicating that the hot melt adhesive can achieve good hydrophilicity and high-temperature bonding performance at the same time by compounding two ethylene-vinyl acetate copolymers with different VA contents.

[0046] Combining Examples 1-5, it can be seen that the melting temperature of the hot melt adhesive of the present invention is low, which is close to the deformation resistance temperature of the lost foam of the foam material, and belongs to the low-temperature hot melt adhesive. When bonding the lost foam of the foam material, the curing time is short, the hot melt adhesive cools down quickly, and the lost foam will not be damaged or deformed, ensuring that the coating layer is flat when the refractory coating is applied to the surface of the lost foam bonding place, and the surface of the metal casting finally obtained is flat without defects.

[0047] It is apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, and the changes still fall within the protection scope of the invention.

Claims

1. A hot melt adhesive for lost foam, characterized in that: The raw materials of the hot melt adhesive include the following components in parts by weight: 5-10 parts of viscosity modifier, 35-45 parts of ethylene-vinyl acetate copolymer, 5-10 parts of hydrophilic agent, 40-50 parts of tackifying resin, 0.05-0.1 parts of color powder and 0.1-1.0 parts of antioxidant.

2. The hot melt adhesive for lost foam according to claim 1, characterized in that: The hydrophilic agent is BASF HL560.

3. The hot melt adhesive for lost foam according to claim 1, characterized in that: The ethylene-vinyl acetate copolymer consists of an A component with a VA content of 31-33% and a B component with a VA content of 18-20%, and the weight ratio of the A component to the B component is 2-4:

1.

4. The hot melt adhesive for lost foam according to claim 1, characterized in that: The viscosity modifier is at least one of Sinopec 58# fully refined paraffin wax and Sinopec 80# microcrystalline wax.

5. The hot melt adhesive for lost foam according to claim 1, characterized in that: The tackifying resin is at least one of Komao rosin resin 146 and Komao KA120.

6. The hot melt adhesive for lost foam according to claim 1, characterized in that: The toner is Meize M169.

7. The hot melt adhesive for lost foam according to claim 1, characterized in that: The antioxidant is at least one of Lianlong 1010 and Lianlong 168.

8. A method for preparing a hot melt adhesive for lost foam, characterized in that: The preparation method is used to prepare a hot melt adhesive for lost foam according to any one of claims 1 to 7, and the preparation method comprises the following steps: 1) Add viscosity regulator and antioxidant to a reaction kettle heated to 90-110°C, stir at a stirring speed of 45-55 rpm, and continue heating to 120-140°C; 2) After all materials in the reactor are melted into liquid, add all the ethylene-vinyl acetate copolymer, stir at a stirring speed of 45-55 rpm, maintain the temperature at 120-140°C and continue to evacuate to -0.08 MPa; 3) After all materials in the reactor are melted evenly, add tackifying resin, color powder and hydrophilic agent, stir at a stirring speed of 45-55 rpm, maintain the temperature at 100-110°C, and continue to evacuate to -0.08 MPa. After all materials are melted evenly, the above-mentioned hot melt adhesive is obtained.

9. Use of the hot melt adhesive as described in any one of claims 1 to 7 in lost foam casting.

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