A polyolefin hot melt adhesive capable of bonding various substrates and its preparation process

Abstract

This invention provides a polyolefin hot melt adhesive capable of bonding various substrates. The raw materials include: 5-15 parts by weight of APAO, 1-15 parts by weight of low-density polyethylene, 1-15 parts by weight of polypropylene, 5-15 parts by weight of modified EVA, 2-16 parts by weight of polar unsaturated monomers, and 4-17 parts by weight of tackifying resin. This hot melt adhesive can be widely used on PVC, ABS, PE, fabrics, leather, wood, and paper, exhibiting excellent bonding performance.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically a polyolefin hot melt adhesive that can bond to various substrates and its preparation process. Background Technology

[0002] Hot melt adhesive is a solvent-free, solid, plastic adhesive made by melting and mixing thermoplastic resin or thermoplastic elastomer as the main component, with added tackifying resin, waxes, plasticizers and fillers. Within a certain temperature range, its physical state changes with temperature, while its chemical properties remain unchanged. It has the advantages of being non-toxic, odorless, environmentally friendly, and easy to prepare, and is considered an environmentally friendly chemical product.

[0003] In recent years, the global annual production of hot melt adhesives has been on an upward trend, with the highest growth rate among all types of adhesives. The variety of products is becoming increasingly diverse, and their applications are becoming more widespread. Among the many types of hot melt adhesives, the two most important and representative are: one is hot melt adhesive based on ethylene-vinyl acetate random copolymer (EVA), or EVA hot melt adhesive for short. EVA hot melt adhesives are the most widely used and consumed type of hot melt adhesive due to their fast curing, lack of pollution, strong adhesion, and the fact that the adhesive layer possesses both flexibility and hardness as well as a certain degree of toughness. Furthermore, their preparation method is simple.

[0004] Another type is polyolefin hot melt adhesive. Compared with EVA hot melt adhesive, its advantages are: 1. It has a lower density, about 0.9, so the same weight of hot melt adhesive can seal more cardboard boxes, theoretically sealing about 8% more, which means it can save more hot melt adhesive; 2. It is cleaner to use, and the carbonization and skinning conditions are much better than EVA hot melt adhesive; 3. Polyolefin hot melt adhesive has good viscosity stability, which is conducive to precise application; 4. It has good color stability and good antioxidant and anti-aging properties.

[0005] Polyolefin hot melt adhesives have poor adhesion to ABS and PC materials and require a long curing time. To address this, the inventors conducted long-term trials and explorations, and published "Adjustment Scheme for the Properties of Polyolefin Hot Melt Adhesives" in Volume 48, Issue 3 of the journal "Chemical Technology and Development" in March 2019. However, this article only focused on adjusting the properties of hot melt adhesives, such as softening point, viscosity, embrittlement temperature, and open time. Summary of the Invention

[0006] The purpose of this invention is to address the problems in the prior art by providing a polyolefin hot melt adhesive that can bond to various substrates and its preparation process.

[0007] To achieve the above objectives, the specific plan is as follows:

[0008] A polyolefin hot melt adhesive that can bond to various substrates comprises the following raw materials: 5-15 parts by weight of APAO, 1-15 parts by weight of low-density polyethylene, 1-15 parts by weight of polypropylene, 5-15 parts by weight of modified EVA, 2-16 parts by weight of polar unsaturated monomer, and 4-17 parts by weight of tackifying resin.

[0009] In a further preferred embodiment of the present invention, the modified EVA is prepared by: 1) adding maleic anhydride to a screw extruder and heating it until the maleic anhydride is completely melted into a liquid, then adding EVA and mixing evenly; 2) adding waterborne polyurethane resin and either polyvinyl alcohol or polyacrylonitrile as the modifier to the screw extruder in step S1, mixing evenly to obtain a masterbatch; 3) mixing and melting the masterbatch obtained in step 2) at 120–180°C for 25–35 min, cooling it, extruding and drawing it into fibers, and granulating it to obtain modified EVA. The modification of EVA introduces polar groups, enhancing its adhesion to polar materials.

[0010] In a further preferred embodiment of the present invention, the weight ratio of the modified EVA raw material is: waterborne polyurethane resin: modified material: maleic anhydride = 10-40:30-50:10-20:6-15.

[0011] In a further preferred embodiment of the present invention, the modified material comprises any one or a mixture of two of polyvinyl alcohol and polyacrylonitrile.

[0012] In a further preferred embodiment of the present invention, the raw materials also include 0.6-7 parts by weight of a coupling agent for melt grafting, which imparts silanoxy groups to the polyolefin hot melt adhesive, thereby enhancing its adhesion to inorganic materials.

[0013] In a further preferred embodiment of the present invention, the raw materials further include 0.2-2 parts by weight of an initiator.

[0014] In a further preferred embodiment of the present invention, the raw materials also include 0.2-2 parts by weight of an antioxidant.

[0015] In a further preferred embodiment of the present invention, the APAO is purchased from Liaoyang Liaohua Qida Chemical Co., Ltd., and is a low molecular weight, high flowability, amorphous, and highly random flexible olefin copolymer obtained by polymerization of α-olefin as raw material.

[0016] In a further preferred embodiment of the present invention, the polypropylene is any one or a combination of two of polypropylene random copolymer and homopolymer polypropylene.

[0017] In a further preferred embodiment of the present invention, the polypropylene random copolymer is formed by random copolymerization of propylene and α-olefin; the density of the polypropylene random copolymer is 0.85-0.95 g / cm³. 3The melt flow index is 2-20 g / 10 min; the number of carbon atoms in the α-olefins of the random copolymer of polypropylene is 4-15, and the α-olefins in the random copolymer of polypropylene account for 1%-8% of their respective mass percentages.

[0018] In a further preferred embodiment of the present invention, the homopolymer polypropylene has 15-60 carbon atoms.

[0019] In a further preferred embodiment of the present invention, the polar unsaturated monomer comprises any one or more combinations of acrylic acid and its esters, methacrylic acid and its esters, acrylonitrile, maleic acid, fumaric acid, itaconic acid, maleic anhydride, 5-norbornene-2,3-dianhydride, itaconic anhydride, and methyl maleic anhydride, thereby giving the polyolefin hot melt adhesive polar groups and enhancing its adhesion to polar materials.

[0020] In a further preferred embodiment of the present invention, the coupling agent comprises any one or a combination of one or more silane coupling agents and titanate coupling agents.

[0021] In a further preferred embodiment of the present invention, the coupling agent is any one or a combination of more than one of KH570, isopropyltris(dioctylpyrophosphoryloxy)titanate, and A151.

[0022] In a further preferred embodiment of the present invention, the tackifying resin comprises one or a combination of rosin resin, terpene resin, petroleum resin, or derivatives thereof.

[0023] In a further preferred embodiment of the present invention, the initiator comprises any one or more of dicumyl peroxide, benzoyl peroxide, ditert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane or tert-butylperoxycarbonate-2-ethylhexyl ester.

[0024] In a further preferred embodiment of the present invention, the antioxidant is either antioxidant 1010 or antioxidant 1098.

[0025] A polyolefin hot melt adhesive that can bond to various substrates is prepared by mixing and melting low-density polyethylene, polypropylene, tackifying resin, and polar unsaturated monomers at 160-180℃, then adding APAO, modified EVA, coupling agent, initiator, and antioxidant, maintaining the temperature at 160-180℃, feeding into a screw extruder, cooling, extruding, and granulating to obtain the polyolefin hot melt adhesive that can bond to various substrates.

[0026] Unlike existing technologies, this invention achieves the following technical effects:

[0027] 1) This invention modifies EVA by introducing polar groups to enhance its adhesion to polar materials.

[0028] 2) The synergistic effect of the modified EVA, APAO and polypropylene random copolymer of the present invention enables the sample prepared by the moisture-curing hot melt adhesive to have excellent bonding strength and certain waterproof performance, and shortens the curing time.

[0029] 3) The hot melt adhesive of the present invention can be widely used in PVC, ABS, PE, fabric, leather, wood and paper, etc., and has good bonding performance. Detailed Implementation

[0030] The technical solutions of the sub-invention will now be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Part One:

[0032] Preparation of modified EVA(D):

[0033] 1) Add maleic anhydride to a screw extruder and heat until the maleic anhydride is completely melted into a liquid. Add EVA and mix thoroughly. 2) In the screw extruder of S1, add waterborne polyurethane resin and modified polyvinyl alcohol, and mix thoroughly to obtain a masterbatch. 3) Mix and melt the masterbatch obtained in 2) at 120-180℃ for 25-35 minutes, cool, extrude into fibers, and granulate to obtain modified EVA(D). The weight ratio of the raw materials is: EVA:waterborne polyurethane resin:polyvinyl alcohol:maleic anhydride = 30:40:10:8.

[0034] Example 1:

[0035] Weigh the following raw materials:

[0036] APAO 600g;

[0037] 120g of low-density polyethylene;

[0038] 150g of random copolymer of polypropylene;

[0039] Modified EVA(D) 120g;

[0040] 80g of polar unsaturated monomer;

[0041] 100g of tackifying resin.

[0042] Preparation process: Low-density polyethylene, random copolymer of polypropylene, tackifying resin and polar unsaturated monomer are mixed and melted at 160-180℃, then APAO and modified EVA(D) are added, the temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled and extruded into granules to obtain the polyolefin hot melt adhesive of Example 1.

[0043] Example 2:

[0044] The raw materials are the same as in Example 1, but with the addition of 10g of coupling agent, 10g of initiator and 10g of antioxidant and other additives.

[0045] The preparation process is as follows: low-density polyethylene, polypropylene random copolymer, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D), coupling agent, initiator and antioxidant are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 2.

[0046] Example 3, raw materials are the same as in Example 2.

[0047] The preparation process was modified as follows: all raw materials were mixed and melted at 160-180℃, and then granulated by cooling through a screw extruder to obtain the polyolefin hot melt adhesive of Example 3.

[0048] Example 4:

[0049] Refer to Examples 1 and 2, but only coupling agents are added to the additives, without initiators and antioxidants.

[0050] The preparation process is as follows: low-density polyethylene, polypropylene random copolymer, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D) and coupling agent are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 4.

[0051] Example 5:

[0052] Refer to Examples 1 and 2, but only initiators are added to the additives, without coupling agents and antioxidants.

[0053] The preparation process is as follows: low-density polyethylene, random copolymer of polypropylene, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D) and initiator are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 5.

[0054] Example 6:

[0055] Refer to Examples 1 and 2, but only antioxidants are added to the additives, without coupling agents and initiators.

[0056] The preparation process is as follows: low-density polyethylene, polypropylene random copolymer, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D) and antioxidant are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 6.

[0057] Example 7:

[0058] Refer to Examples 1 and 2, but only initiators and coupling agents are added to the additives, without antioxidants.

[0059] The preparation process is as follows: low-density polyethylene, polypropylene random copolymer, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D), initiator and coupling agent are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 7.

[0060] Example 8:

[0061] Refer to Examples 1 and 2, but only initiators and antioxidants are added to the additives, without coupling agents.

[0062] The preparation process is as follows: low-density polyethylene, polypropylene random copolymer, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D), initiator and antioxidant are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 8.

[0063] Example 9:

[0064] Refer to Examples 1 and 2, but only coupling agents and antioxidants are added to the adjuvants, without initiators.

[0065] The preparation process is as follows: low-density polyethylene, polypropylene random copolymer, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180℃, and then APAO, modified EVA(D), coupling agent and antioxidant are added. The temperature is maintained at 160-180℃, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive of Example 9.

[0066] The polyolefin hot melt adhesives prepared in Examples 1-9 were subjected to performance tests. The test standard was: melt viscosity reference.

[0067] ASTM D3236; Low-temperature flexibility reference standard ASTM D3111; Elongation at break reference standard ISO 527; Shore hardness reference standard ISO 868; Melting point reference standard ISO 3146; Curing time reference standard ASTM D4497.

[0068]

[0069] The data above shows that the hot melt adhesives in Examples 1-9 have moderate melt viscosity and short curing time, making them suitable for industrial use. When the hot melt adhesives prepared in Examples 1-9 were tested in an environment with 97% humidity and 75°C, some of the bonded leather and fabric showed slight delamination after 72 hours.

[0070] Part Two:

[0071] The preparation of modified EVA(D) is described in Part 1.

[0072] The raw materials for Examples 10-18 are shown in the table below:

[0073]

[0074]

[0075] The preparation processes of Examples 10-18 correspond one-to-one with those of Examples 1-9. For example, Example 10 corresponds to Example 1, Example 11 corresponds to Example 2, and so on.

[0076] The hot melt adhesives prepared in Examples 10-18 were subjected to performance tests. The melt viscosity, low-temperature flexibility, elongation at break, and curing time were similar to those in Examples 1-9. However, in the application test of the hot melt adhesives prepared in Examples 10-18, the bonded leather and fabric completely delaminated after 72 hours in an environment with 97% humidity and 75°C. Therefore, the inventors speculate that the mixing of polypropylene random copolymer and polypropylene homopolymer has a significant promoting effect on the moisture resistance of the hot melt adhesive.

[0077] Part Three:

[0078] Preparation of modified EVA(E):

[0079] 1) Add maleic anhydride to a screw extruder and heat until the maleic anhydride is completely melted into a liquid. Add EVA and mix thoroughly. 2) In the screw extruder of S1, add waterborne polyurethane resin and modified polyacrylonitrile, and mix thoroughly to obtain a masterbatch. 3) Mix and melt the masterbatch obtained in 2) at 120-180℃ for 25-35 minutes, cool, extrude, draw into fibers, and granulate to obtain modified EVA(E). The weight ratio of the raw materials is: waterborne polyurethane resin: polyvinyl alcohol: maleic anhydride = 60:20:10:10.

[0080] The weight proportions of each raw material in Examples 19-27 are shown in the table below:

[0081]

[0082] The preparation processes of Examples 19-27 correspond one-to-one with the preparation processes of Examples 10-18 and Examples 1-9. For example, Example 19 corresponds to Examples 1 and 10, Example 20 corresponds to Examples 11 and 2, and so on.

[0083] The properties of the hot melt adhesives prepared in Examples 10-18 were tested, and the results are shown in the table below:

[0084]

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polyolefin hot melt adhesive capable of bonding various substrates, comprising the following raw materials: The mixture comprises 5-15 parts by weight of APAO, 1-15 parts by weight of low-density polyethylene, 1-15 parts by weight of polypropylene, 5-15 parts by weight of modified EVA, 2-16 parts by weight of polar unsaturated monomer, and 4-17 parts by weight of tackifying resin. The modified EVA is prepared by the following method: 1) Maleic anhydride is added to a screw extruder and heated until the maleic anhydride is completely melted into a liquid. EVA is then added and mixed evenly. 2) In the screw extruder of S1, waterborne polyurethane resin and either polyvinyl alcohol or polyacrylonitrile as the modified material are added and mixed evenly to obtain a masterbatch. 3) The masterbatch obtained in step 2) is mixed and melted at 120-180°C for 25-35 minutes. After cooling, it is extruded, drawn into fibers, and granulated to obtain modified EVA.

2. The polyolefin hot melt adhesive capable of bonding multiple substrates according to claim 1, characterized in that: The weight ratio of the modified EVA raw material components is: EVA: waterborne polyurethane resin: modified material: maleic anhydride = 10-40:30-50:10-20:6-15.

3. The polyolefin hot melt adhesive capable of bonding multiple substrates according to claim 1, characterized in that: The raw materials also include 0.6-7 parts by weight of coupling agent.

4. The polyolefin hot melt adhesive capable of bonding multiple substrates according to claim 1, characterized in that: The raw materials also include 0.2-2 parts by weight of initiator.

5. The polyolefin hot melt adhesive capable of bonding multiple substrates according to claim 1, characterized in that: The raw materials also include 0.2-2 parts by weight of antioxidants.

6. The polyolefin hot melt adhesive capable of bonding multiple substrates according to claim 1, characterized in that: The polypropylene is any one or a combination of two of the following: random copolymer of polypropylene and homopolymer polypropylene.

7. The polyolefin hot melt adhesive capable of bonding multiple substrates according to claim 6, characterized in that: The random copolymer of polypropylene is formed by random copolymerization of propylene and α-olefin; the density of the random copolymer of polypropylene is 0.85-0.95 g / cm³. 3 The melt flow index is 2-20 g / 10 min; the number of carbon atoms in the α-olefin of the polypropylene random copolymer is 4-15, and the α-olefin in the polypropylene random copolymer accounts for 1%-8% of the mass percentage of the polypropylene random copolymer.

8. The preparation process of the polyolefin hot melt adhesive capable of bonding multiple substrates according to any one of claims 1-7 is as follows: low-density polyethylene, polypropylene, tackifying resin, and polar unsaturated monomer are mixed and melted at 160-180°C, and then APAO, modified EVA, coupling agent, initiator and antioxidant are added. The temperature is maintained at 160-180°C, and the mixture is fed into a screw extruder, cooled, extruded and granulated to obtain the polyolefin hot melt adhesive capable of bonding multiple substrates.

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