Polymer PUR (Polyurethane) hot melt adhesive with high initial viscosity

Abstract

The invention discloses a macromolecular PUR (Polyurethane) hot melt adhesive with high initial viscosity, and relates to the technical field of hot melt adhesives. The high-initial-viscosity polymer PUR hot melt adhesive comprises the following components in parts by weight: 120-160 parts of isocyanate, 45-65 parts of a polyol compound, 30-50 parts of a catalyst, 2-6 parts of a solvent or a diluent and 3-8 parts of other additives, and is prepared by the following steps: adding the polyol compound and a part of isocyanate into a reaction kettle, and heating and stirring to obtain a first prepolymer; adding the modified polyester polyol and the balance of isocyanate into the reaction kettle, and heating and stirring to obtain a second prepolymer; the molecular weight of the rubber matrix is high, so that the polymerized rubber matrix is good in cohesiveness, melt flow, impact resistance and bending resistance.

Description

Technical Field

[0001] The invention relates to the technical field of hot melt adhesives, in particular to a high-initial-viscosity polymer PUR hot melt adhesive. Background Art

[0002] Hot melt adhesive is a plastic adhesive. Its physical state changes with temperature within a certain temperature range, but its chemical properties remain unchanged. It is non-toxic and tasteless, and is an environmentally friendly chemical product. It is popular because the product itself is solid, easy to package, transport, store, solvent-free, pollution-free, non-toxic; and has the advantages of simple production process, high added value, high bonding strength, and fast speed.

[0003] The invention with the prior art publication number CN112322248B relates to a PUR hot melt adhesive for composite panels and a preparation method thereof, comprising 60 to 80 parts of a polyol polymer, 25 to 35 parts of a polyisocyanate, 20 to 30 parts of a thermoplastic resin, 1 to 3 parts of a silane coupling agent, and 1 to 7 parts of other additives. The polyol polymer, by mass percentage, comprises 10 to 15% of a crystalline polyester polyol, 30 to 45% of a non-crystalline polyester polyol, 20 to 40% of a polypropylene glycol, and 20 to 35% of a castor oil-modified polyol. The provided PUR hot melt adhesive for composite panels has the characteristics of high initial adhesion and final adhesion; excellent heat resistance, hydrolysis resistance, and aging resistance. In the present invention, the mixed use of crystalline polyester polyol, non-crystalline polyester polyol, polypropylene glycol, and castor oil-modified polyol is used to make the PUR hot melt adhesive have good tensile properties, wear resistance, flexibility, heat resistance, and initial adhesion.

[0004] However, the above-mentioned PUR hot melt adhesive for composite panels still has the following problems when used: from the molecular structure point of view, the saturated polyester molecules of its colloid are low molecular weight, and some alcohols are added during synthesis to replace part of the original monomers to cause random polymerization, thereby destroying the crystallinity, improving the wettability and bonding strength, but due to its low molecular weight, its adhesion, melt flow, impact resistance and flexural resistance are average.

[0005] To this end, we have developed a new high initial viscosity polymer PUR hot melt adhesive. Summary of the invention

[0006] To achieve the above objectives, the present invention is implemented through the following technical scheme: a high molecular weight PUR hot melt adhesive with high initial viscosity, comprising, by weight, 120 to 160 parts of isocyanate, 20 to 30 parts of modified polyester polyol, 45 to 65 parts of polyol compound, 30 to 50 parts of catalyst, 2 to 6 parts of solvent or diluent, and 3 to 8 parts of other additives. The polyol compound and a part of the isocyanate are added to a reactor, heated and stirred to obtain a first prepolymer, and the modified polyester polyol and the remaining isocyanate are added to a reactor, heated and stirred to obtain a second prepolymer.

[0007] Preferably, the isocyanate is a component of the polyurethane glue, accounting for 40%-60% of the total formula, providing the isocyanate groups required for the polymerization reaction, so that the polyurethane prepolymer forms a heat-resistant, corrosion-resistant, and high-hardness adhesive. The polyol compound is another important component of the polyurethane glue, usually accounting for 20%-30% of the total formula. They include polyesters, polyethers, etc., which can provide hydroxyl groups in the reaction and react with isocyanate to produce polyurethane chains.

[0008] Preferably, the catalyst is used to accelerate the hardening reaction and promote the cross-linking reaction of isocyanate and polyol. The main types of catalysts include organic tin, organic lead, and diamine. The solvent or diluent can adjust the viscosity and solid content of the glue and is usually used in one-component PUR glue. The polyurethane glue can also be added with other additives, such as surfactants, fillers, pigments, antioxidants, etc., to improve its physical properties and usage characteristics.

[0009] Preferably, the polyol compound is a general term for ester groups (-CO-O-) on the main chain of the polymer, which are divided into two categories: unsaturated polyester and thermoplastic polyester. The hot melt adhesive requires linear saturated polyester resin, which is prepared by transesterification, esterification and polycondensation of polyacids and polyols.

[0010] Preferably, the polyol compound is usually made of dimethyl terephthalate, isophthalic acid, hexanediol and butanediol, etc. The molar ratio of the acid and the alcohol in the polyol compound determines the end group of the polyester molecule.

[0011] Preferably, the polyester molecules obtained when the acid is in excess have carboxyl terminal groups, and the polyester molecules obtained when the alcohol is in excess have hydroxyl terminal groups. The synthesis of the polyester molecules is generally divided into two steps: first, a polyester prepolymer is prepared, and then a high molecular weight polyester is synthesized from the prepolymer.

[0012] Preferably, the PUR hot melt adhesive provides strong, durable bonding and is suitable for a variety of materials, including wood, metal, and plastic, and the high strength of the PUR hot melt adhesive enables it to perform well in applications that require a certain amount of tensile or shear force.

[0013] Preferably, the PUR hot melt adhesive has a certain elasticity and can maintain adhesion when the material moves or deforms. This elasticity also gives it excellent impact resistance, making it widely used in applications that require durability.

[0014] Preferably, the PUR hot melt adhesive cures quickly after the application of a heat source and can form a strong connection within seconds, which makes it very suitable for efficient and fast production lines.

[0015] Preferably, the PUR hot melt adhesive can usually withstand relatively high temperatures after curing, which makes it perform well in some special applications, such as automobile manufacturing.

[0016] Preferably, the PUR hot melt adhesive, due to its liquid state, is able to fill irregular shapes and surfaces, providing an excellent sealing effect and preventing liquid or gas penetration.

[0017] Beneficial Effects

[0018] The present invention provides a high molecular weight PUR hot melt adhesive with high initial viscosity. It has the following beneficial effects:

[0019] (1) The high molecular weight PUR hot melt adhesive with high initial viscosity is prepared by adding the polyol compound and a part of the isocyanate into a reaction kettle, heating and stirring to obtain a first prepolymer, and then adding the modified polyester polyol and the remaining amount of the isocyanate into the reaction kettle, heating and stirring to obtain a second prepolymer. The molecular weight of the adhesive matrix is ​​relatively high, and the adhesiveness, melt flow, impact resistance and flexural resistance after polymerization are good.

[0020] (2) This high initial viscosity polymer PUR hot melt adhesive is prepared by using dimethyl terephthalate, polytetramethylene glycol ether and 4-butanediol to obtain a polyether polyester copolymer through an ester exchange reaction. The copolymer consists of two soft and hard blocks, has good melt flowability, impact resistance, and flex resistance, and is widely used. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Embodiment 1:

[0023] The invention provides a high-initial-viscosity polymer PUR hot-melt adhesive, which comprises, by weight, 120-160 parts of isocyanate, 20-30 parts of modified polyester polyol, 45-65 parts of polyol compound, 30-50 parts of catalyst, 2-6 parts of solvent or diluent, and 3-8 parts of other additives. The polyol compound and a part of the isocyanate are added into a reaction kettle, and heated and stirred to obtain a first prepolymer. The modified polyester polyol and the rest of the isocyanate are added into the reaction kettle, and heated and stirred to obtain a second prepolymer. The molecular weight of the adhesive matrix is ​​relatively high, and the adhesiveness, melt flow, impact resistance and flex resistance after polymerization are good.

[0024] Isocyanate is a component of polyurethane adhesive, accounting for 40%-60% of the total formula. It provides the isocyanate groups required for the polymerization reaction, allowing the polyurethane prepolymer to form a heat-resistant, corrosion-resistant, and high-hardness adhesive. Polyol compounds are another important component of polyurethane adhesive, usually accounting for 20%-30% of the total formula. They include polyesters, polyethers, etc., which can provide hydroxyl groups in the reaction and react with isocyanate to produce polyurethane chains.

[0025] Catalysts are used to accelerate the hardening reaction and promote the cross-linking reaction of isocyanate and polyol. The main types of catalysts include organic tin, organic lead, and diamine. Solvents or diluents can adjust the viscosity and solid content of the glue. They are usually used in one-component PUR glue. Polyurethane glue can also add other additives, such as surfactants, fillers, pigments, antioxidants, etc., to improve its physical properties and usage characteristics.

[0026] Polyol compounds are a general term for polymers containing ester groups (-CO-O-) on the main chain. They are divided into two categories: unsaturated polyesters and thermoplastic polyesters. What hot melt adhesives need is linear saturated polyester resins, which are made from polyacids and polyols through ester exchange reactions, esterification reactions and condensation reactions.

[0027] Polyol compounds usually use dimethyl terephthalate, isophthalic acid, hexanediol and butanediol as raw materials. The molar ratio of the acid and alcohol in the polyol compounds determines the end group of the polyester molecule.

[0028] The terminal group of the polyester molecule obtained when the acid is in excess is a carboxyl group, and the terminal group of the polyester molecule obtained when the alcohol is in excess is a hydroxyl group. The synthesis of polyester molecules is generally divided into two steps: first, a polyester prepolymer is prepared, and then a high molecular weight polyester is synthesized from the prepolymer.

[0029] PUR hot melt adhesive provides strong, long-lasting bonding and is suitable for a variety of materials, including wood, metal, and plastic. The high strength of PUR hot melt adhesive enables it to perform well in applications that need to withstand certain tensile or shear forces. PUR hot melt adhesive has a certain elasticity and can maintain adhesion when the material moves or deforms. This elasticity also gives it excellent impact resistance, making it widely used in applications that require durability.

[0030] PUR hot melt adhesive cures quickly after the heat source is applied, and can form a strong connection within seconds, which makes it very suitable for efficient and fast production lines. PUR hot melt adhesive can usually withstand quite high temperatures after curing, which makes it excellent in some special applications such as automotive manufacturing. Due to its liquid state, PUR hot melt adhesive can fill irregular shapes and surfaces, providing excellent sealing effect and preventing liquid or gas penetration.

[0031] Embodiment 2:

[0032] The difference between this embodiment and the first embodiment is that the polyester hot melt adhesive has good bonding strength and heat resistance, cold resistance, dry and wet cleaning resistance, and excellent electrical properties. The disadvantage is the viscosity when heated and melted, which is difficult to operate manually and generally requires special coating equipment for construction.

[0033] From the chemical structure point of view, polyester hot melt adhesives are divided into copolyesters, polyether polyesters, and polyamide polyesters.

[0034] From the perspective of molecular structure, the introduction of phenyl groups into the molecular straight chain of saturated polyester will increase its melting point, tensile strength and heat resistance, and the introduction of alkyl and ether bonds will improve melt viscosity, flexibility and toughness, but this molecular structure also has high crystallinity, poor wettability and bonding strength;

[0035] Therefore, some acids or alcohols are usually added during the synthesis to replace part of the original monomers, causing them to undergo random polymerization, thereby destroying the crystallinity and improving the wettability and bonding strength.

[0036] The polyether polyester copolymer is prepared by ester exchange reaction using dimethyl terephthalate, polytetramethylene glycol ether and 4-butanediol. The copolymer consists of soft and hard blocks, has good melt flowability, impact resistance, flex resistance, and is widely used.

[0037] Embodiment three:

[0038] The difference between this embodiment and embodiments 1 and 2 is that the ratio of the polyester hot melt adhesive matrix to other additives is not strict. The main function of the additives is to reduce the melt viscosity. Commonly used diluents include polystyrene resin and petroleum grease, tackifiers include xylene resin and phenol resin, and fillers include talcum powder and calcium carbonate. Sometimes, in order to adapt to different working conditions, it is necessary to add reinforcing agents (glass fiber, C fiber, etc.), flame retardants (brominated aromatic compounds, phosphorus compounds), ultraviolet absorbers (diphenyl ketone compounds), etc. Polyester hot melt adhesive can be made into powder, granules, strips, etc., and generally uses special coating equipment.

[0039] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high molecular weight PUR hot melt adhesive with high initial viscosity, characterized by: In parts by weight, it comprises 120 to 160 parts of isocyanate, 20 to 30 parts of modified polyester polyol, 45 to 65 parts of polyol compound, 30 to 50 parts of catalyst, 2 to 6 parts of solvent or diluent, and 3 to 8 parts of other additives; Adding the polyol compound and a portion of the isocyanate into a reaction kettle, performing heating and stirring operations, to obtain a first prepolymer; Adding the modified polyester polyol and the remaining amount of the isocyanate into a reaction kettle, performing heating and stirring operations to obtain a second prepolymer; The isocyanate is a component of the polyurethane adhesive, accounting for 40%-60% of the total formula, and provides the isocyanate groups required for the polymerization reaction; The polyol compound is another important component of polyurethane adhesive, including polyester, polyether, etc. The catalyst promotes the cross-linking reaction of isocyanate and polyol, and includes organic tin, organic lead, and diamine; The solvent or diluent is used in the one-component PUR adhesive; The polyurethane adhesive may also be added with other additives.

2. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The polyol compounds are a general term for polymers containing ester groups (-CO-O-) on the main chain; The hot melt adhesive requires a linear saturated polyester resin, which is prepared by ester exchange reaction, esterification reaction and polycondensation reaction of polyacid and polyol.

3. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The polyol compound is usually made of dimethyl terephthalate, isophthalic acid, hexanediol and butanediol.

4. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The molar ratio of the acid and alcohol of the polyol compound determines the end groups of the polyester molecules; When the acid is in excess, the polyester molecules obtained have carboxyl terminal groups, and when the alcohol is in excess, the polyester molecules obtained have hydroxyl terminal groups; The synthesis of the polyester molecule is generally divided into two steps: first, a polyester prepolymer is prepared, and then a high molecular weight polyester is synthesized from the prepolymer.

5. The high molecular weight PUR hot melt adhesive with high initial viscosity according to claim 1, characterized in that: The PUR hot melt adhesive provides a strong, durable bond and is suitable for a variety of materials.

6. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The PUR hot melt adhesive has certain elasticity.

7. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The PUR hot melt adhesive can be cured quickly after applying a heat source.

8. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The PUR hot melt adhesive can usually withstand relatively high temperatures after curing.

9. The high initial viscosity polymer PUR hot melt adhesive according to claim 1, characterized in that: The PUR hot melt adhesive is able to fill irregular shapes and surfaces due to its liquid state.