Natural rubber type hot melt glue and preparation method thereof

Abstract

The invention discloses natural rubber type hot melt glue and a preparation method thereof. The natural rubber type hot melt glue comprises the following components in percentage by weight: 40%-60% of natural rubber, 5%-15% of EVA (Ethylene Vinyl Acetate) resin, 40%-60% of tackifying resin, 5%-10% of a softening agent, 1%-2% of an anti-aging agent and 0.1%-0.2% of a cross-linking agent. According to the natural rubber type hot melt glue, the EVA resin is added at the front end of the kneaded natural rubber, so that the effect similar to that of a plasticizer is achieved, and the friction chain scission effect generated in the kneading process of rubber molecules is greatly reduced; the completeness of a natural rubber molecular chain is reserved, other components can be better fused with natural rubber macromolecules, and residual glue is not easy to remain in the hot-melt glue. In addition, the natural rubber type hot melt glue is simple in preparation method, low in preparation cost and suitable for industrial mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of glue, and in particular relates to a natural rubber type hot melt glue and a preparation method thereof. Background Art

[0002] Hot melt adhesive is a kind of glue made by heating and melting at high temperature with SBC as the skeleton, adding tackifying resin and rubber oil. Hot melt adhesive is widely used because it is solvent-free, has high production efficiency and low production cost, but it often has problems such as solvent resistance, poor temperature resistance and poor adhesion to non-polar surfaces. Some hot melt adhesives use natural rubber with better temperature resistance as the skeleton to replace SBC synthetic rubber to produce hot melt adhesive, but natural rubber has a unique network structure and thermal stability and is a highly elastic polymer material with no fixed melting point. Heating will only soften and degrade it, but will not melt. Moreover, the rubber molecular chains are connected to each other by chemical bonds to form a stable network system. This structure makes the rubber not show fluidity like linear polymers when heated, so it will not melt. In addition, natural rubber begins to degrade at around 200°C and will be completely carbonized at more than 400°C, which means that rubber will decompose instead of melt at high temperatures. Therefore, the common processing method of natural rubber is to dissolve it with a solvent and then apply it, which often brings about problems such as high energy consumption and solvent volatilization pollution.

[0003] Chinese patent CN102167782B discloses a method of grafting monomers such as styrene and methyl methacrylate on the molecular structure of natural rubber to make thermoplastic natural rubber. However, this method cannot effectively reduce the hot melt viscosity of natural rubber, and processing is still difficult. Chinese patent CN1058850561A discloses a method of cutting natural rubber into a suitable molecular weight and grafting thermoplastic polymer molecules on the side chains to make the natural rubber have thermoplastic function, but this method is only suitable for preparing a small amount of samples in the laboratory due to high cost and complicated operation, and is not suitable for large-scale production.

[0004] The above methods have not been widely used due to the problem of preparation cost, the inability to effectively solve the hot melt viscosity problem, or the problem of inability to mass produce.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a natural rubber type hot melt adhesive, the hot melt viscosity of which is improved and it is not easy to leave residual adhesive.

[0007] In order to achieve the above-mentioned purpose, the technical solution provided by a specific embodiment of the present invention is as follows: a natural rubber type hot melt adhesive, which includes the following components in terms of weight percentage: 40%-60% natural rubber, 5%-15% EVA resin, 40%-60% tackifying resin, 5%-10% softener, 1%-2% antioxidant and 0.1%-0.2% cross-linking agent.

[0008] In one or more embodiments of the present invention, the natural rubber is selected from 3L rubber with a Mooney viscosity between 50-80, constant viscosity CV rubber and white wrinkle rubber.

[0009] In one or more embodiments of the present invention, the VA content of the EVA resin is between 10% and 25%.

[0010] In one or more embodiments of the present invention, the tackifying resin is selected from one or more of rosin resin, terephthalate resin and petroleum resin.

[0011] In one or more embodiments of the present invention, the petroleum resin is selected from one or more of C5 petroleum resin, C9 petroleum resin, C5-C9 copolymerized petroleum resin, styrene resin, dicyclopentadiene resin, pentaerythritol ester resin and hydrogenated resin.

[0012] In one or more embodiments of the present invention, the softener is selected from one of naphthenic oil, white oil and liquid polyisobutylene.

[0013] In one or more embodiments of the present invention, the antioxidant is selected from one or more of phenolic antioxidants, amine antioxidants, heterocyclic antioxidants, peroxide decomposition antioxidants and organophosphorus antioxidants.

[0014] In one or more embodiments of the present invention, the cross-linking agent is selected from isocyanate cross-linking agents.

[0015] Another specific embodiment of the present invention provides a technical solution as follows: a method for preparing a natural rubber type hot melt adhesive, comprising:

[0016] The twin-screw kneading machine is heated to 100-120° C., natural rubber, EVA resin and antioxidant are put into the machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the natural rubber decreases and is melt-mixed with the EVA resin to form a first mixture;

[0017] The twin-screw kneading machine is further heated to 150-170° C., tackifying resin is added to the first mixture in batches, and the tackifying resin and the first mixture are fully melted to form a second mixture;

[0018] Diluting the crosslinking agent with a softener and adding the crosslinking agent to the second mixture in batches, and fully melting the crosslinking agent and the second mixture to obtain the natural rubber type hot melt adhesive;

[0019] The invention comprises the following components according to weight percentage: 40%-60% natural rubber, 5%-15% EVA resin, 40%-60% tackifying resin, 5%-10% softener, 1%-2% antioxidant and 0.1%-0.2% crosslinking agent.

[0020] In one or more embodiments of the present invention, the amount of the tackifying resin added to the first mixture each time is less than or equal to 20% of the total amount of the tackifying resin.

[0021] Compared with the prior art, the natural rubber type hot melt adhesive of the present invention achieves a similar effect to that of a plasticizer by adding EVA to the front end of the kneaded natural rubber, greatly reducing the friction chain breaking effect of the rubber molecules during the kneading process, and better retaining the integrity of the natural rubber molecular chain. After pretreatment in this way, other components can be better blended with the natural rubber macromolecules, and the prepared natural rubber type hot melt adhesive is not easy to leave residual glue during the application process. In addition, the preparation method of the natural rubber type hot melt adhesive is simple, the preparation cost is low, and it is suitable for mass production. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solutions in the present invention, 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 the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0023] A natural rubber type hot melt adhesive in one embodiment of the present invention comprises the following components in terms of weight percentage: 40%-60% natural rubber, 5%-15% EVA resin, 40%-60% tackifying resin, 5%-10% softener, 1%-2% antioxidant and 0.1%-0.2% cross-linking agent.

[0024] In the above embodiment, the natural rubber type hot melt adhesive of the present invention achieves a similar effect to that of a plasticizer by adding EVA resin at the front end of kneading natural rubber, thereby greatly reducing the friction chain breaking effect of rubber molecules during the kneading process, better retaining the integrity of the natural rubber molecular chain and allowing other components to be better fused with the natural rubber macromolecules, and the hot melt adhesive is not prone to leaving residual glue.

[0025] In one embodiment, the natural rubber can be selected from one of 3L rubber with a Mooney viscosity between 50-80, CV rubber and white wrinkle rubber. The content ratio of VA (vinyl acetate) in the EVA resin is between 10% and 25%. In one embodiment, the tackifying resin is selected from one or more of rosin resin, terephthalate resin and petroleum resin. Preferably, the petroleum resin can be selected from one or more of C5 petroleum resin, C9 petroleum resin, C5-C9 copolymerized petroleum resin, styrene resin, dicyclopentadiene resin, pentaerythritol ester resin and hydrogenated resin. In one embodiment, the softener can be selected from one of cycloalkane oil, white oil and liquid polyisobutylene. The antioxidant can be selected from one or more of phenolic antioxidants, amine antioxidants, heterocyclic antioxidants, peroxide decomposition antioxidants and organophosphorus antioxidants. The crosslinking agent is selected from isocyanate crosslinking agents.

[0026] A method for preparing natural rubber hot melt adhesive in another embodiment of the present invention includes steps S1-S3.

[0027] Step S1: heating the twin-screw kneading machine to 100-120° C., putting natural rubber, EVA resin and antioxidant into the machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the natural rubber decreases and is melted with the EVA resin to form a first mixture.

[0028] Specifically, in step S1, in order to pretreat the natural rubber, the twin-screw kneading machine is first heated to 100-120°C, and then the natural rubber, part of the EVA resin and the antioxidant are put into the twin-screw kneading machine for heating. When the EVA resin begins to soften, the screw kneading is performed, and the viscosity of the natural rubber decreases and is melted with the EVA resin to form a first mixture.

[0029] The natural rubber is selected from 3L rubber with a Mooney viscosity of 50-80, CV rubber and white wrinkle rubber. The VA content of the EVA resin is between 10% and 25%. The antioxidant is selected from one or more of phenolic antioxidants, amine antioxidants, heterocyclic antioxidants, peroxide decomposition antioxidants and organophosphorus antioxidants.

[0030] Step S2: continue to heat the twin-screw kneading machine to 150-170° C., add tackifying resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0031] Specifically, in step S2, the twin-screw kneading machine is further heated to 150-170°C, tackifying resin is added to the first mixture in batches, and the tackifying resin and the first mixture are fully melted to form a second mixture. And the amount of tackifying resin added to the first mixture each time is less than or equal to 20% of the total amount of tackifying resin. The tackifying resin is selected from one or more of rosin resin, terephthalate resin and petroleum resin. Preferably, the petroleum resin can be selected from one or more of C5 petroleum resin, C9 petroleum resin, C5-C9 copolymerized petroleum resin, styrene resin, dicyclopentadiene resin, pentaerythritol ester resin and hydrogenated resin.

[0032] Step S3: diluting the crosslinking agent with a softener and adding the mixture in batches to the second mixture, and fully melting the crosslinking agent and the second mixture to obtain a natural rubber type hot melt adhesive. The natural rubber type hot melt adhesive comprises the following components by weight percentage: 40%-60% natural rubber, 5%-15% EVA resin, 40%-60% tackifying resin, 5%-10% softener, 1%-2% antioxidant and 0.1%-0.2% crosslinking agent.

[0033] Specifically, in step S3, the crosslinking agent is diluted with a softener and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain a natural rubber type hot melt adhesive. The crosslinking agent and the softener are added in batches to prevent the softener from forming an oil film on the rubber surface due to excessive single addition, which hinders the screw shearing. The softener is selected from one of cyclohexane oil, white oil and liquid polyisobutylene. The crosslinking agent is selected from an isocyanate crosslinking agent.

[0034] The present invention is further described below in conjunction with specific embodiments and comparative examples.

[0035] Example 1

[0036] Components: Natural rubber: 40 parts by mass of 3L rubber with a Mooney value of 50. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. EVA resin: 10 parts by mass of EVA resin with a VA content of 19%. Softener: 10 parts by mass of white oil. Antiaging agent: 1.8 parts by mass of phenolic antioxidant. Crosslinking agent: 0.2 parts by mass of isocyanate crosslinking agent.

[0037] preparation:

[0038] S1: First, the twin-screw kneading machine is heated to 100° C., and then 40 parts by weight of 3L rubber with a Mooney value of 50, 10 parts by weight of EVA resin with a VA content of 19% and 1.8 parts by weight of phenolic antioxidant are put into the twin-screw kneading machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the 3L rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0039] S2: Continue to heat the twin-screw kneading machine to 150° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0040] S3: 0.2 parts by mass of isocyanate crosslinking agent is diluted with 10 parts by mass of white oil and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain natural rubber type hot melt adhesive.

[0041] Example 2

[0042] Components: Natural rubber: 40 parts by mass of 3L rubber with a Mooney value of 60. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. EVA resin: 10 parts by mass of EVA resin with a VA content of 19%. Softener: 10 parts by mass of white oil. Antiaging agent: 1.8 parts by mass of phenolic antioxidant. Crosslinking agent: 0.2 parts by mass of isocyanate crosslinking agent.

[0043] preparation:

[0044] S1: First, the twin-screw kneading machine is heated to 105° C., and then 40 parts by weight of 3L rubber with a Mooney value of 60, 10 parts by weight of EVA resin with a VA content of 19% and 1.8 parts by weight of phenolic antioxidant are put into the twin-screw kneading machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the 3L rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0045] S2: Continue to heat the twin-screw kneading machine to 155° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0046] S3: 0.2 parts by mass of isocyanate crosslinking agent is diluted with 10 parts by mass of white oil and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain natural rubber type hot melt adhesive.

[0047] Example 3

[0048] Components: Natural rubber: 40 parts by mass of 3L rubber with a Mooney value of 70. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. EVA resin: 10 parts by mass of EVA resin with a VA content of 19%. Softener: 10 parts by mass of white oil. Antiaging agent: 1.8 parts by mass of amine antioxidant. Crosslinking agent: 0.2 parts by mass of isocyanate crosslinking agent.

[0049] preparation:

[0050] S1: First, the twin-screw kneading machine is heated to 115° C., and then 40 parts by weight of 3L rubber with a Mooney value of 70, 10 parts by weight of EVA resin with a VA content of 19% and 1.8 parts by weight of amine antioxidant are put into the twin-screw kneading machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the 3L rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0051] S2: Continue to heat the twin-screw kneading machine to 160° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0052] S3: 0.2 parts by mass of isocyanate crosslinking agent is diluted with 10 parts by mass of white oil and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain natural rubber type hot melt adhesive.

[0053] Example 4

[0054] Components: Natural rubber: 40 parts by mass of white wrinkled rubber with a Mooney value of 70. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. EVA resin: 10 parts by mass of EVA resin with a VA content of 19%. Softener: 10 parts by mass of white oil. Antiaging agent: 1.8 parts by mass of phenolic antioxidant. Crosslinking agent: 0.2 parts by mass of isocyanate crosslinking agent.

[0055] preparation:

[0056] S1: First, the twin-screw kneading machine is heated to 120°C, and then 40 parts by weight of white crumpled rubber with a Mooney value of 70, 10 parts by weight of EVA resin with a VA content of 19% and 1.8 parts by weight of amine antioxidant are put into the twin-screw kneading machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the white crumpled rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0057] S2: Continue to heat the twin-screw kneading machine to 165° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0058] S3: 0.2 parts by mass of isocyanate crosslinking agent is diluted with 10 parts by mass of white oil and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain natural rubber type hot melt adhesive.

[0059] Example 5

[0060] Components: Natural rubber: 40 parts by mass of CV60 rubber with a Mooney value of 60. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. EVA resin: 10 parts by mass of EVA resin with a VA content of 19%. Softener: 10 parts by mass of white oil. Antiaging agent: 1.8 parts by mass of phenolic antioxidant. Crosslinking agent: 0.2 parts by mass of isocyanate crosslinking agent.

[0061] preparation:

[0062] S1: First, the twin-screw kneading machine is heated to 120° C., and then 40 parts by weight of a constant viscosity CV60 rubber with a Mooney value of 60, 10 parts by weight of an EVA resin with a VA content of 19% and 1.8 parts by weight of an amine antioxidant are put into the twin-screw kneading machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the constant viscosity CV60 rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0063] S2: Continue to heat the twin-screw kneading machine to 170° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0064] S3: 0.2 parts by mass of isocyanate crosslinking agent is diluted with 10 parts by mass of white oil and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain natural rubber type hot melt adhesive.

[0065] Comparative Example 1

[0066] Components: Natural rubber: 40 parts by mass of CV60 rubber with a Mooney value of 60. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. EVA resin: 10 parts by mass of EVA resin with a VA content of 19%. Softener: 10 parts by mass of white oil. Antioxidant: 1.8 parts by mass of phenolic antioxidant.

[0067] preparation:

[0068] S1: First, the twin-screw kneading machine is heated to 120° C., and then 40 parts by weight of a constant viscosity CV60 rubber with a Mooney value of 60, 10 parts by weight of an EVA resin with a VA content of 19% and 1.8 parts by weight of a phenolic antioxidant are put into the twin-screw kneading machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the constant viscosity CV60 rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0069] S2: Continue to heat the twin-screw kneading machine to 165° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0070] S3: 10 parts by mass of white oil is diluted and added to the second mixture and fully melted to obtain hot melt adhesive.

[0071] Comparative Example 2

[0072] Components: Natural rubber: 40 parts by mass of 3L rubber with a Mooney value of 60. Tackifying resin: 20 parts by mass of rosin resin, 18 parts by mass of C5 petroleum resin. Softener: 10 parts by mass of white oil. Antiaging agent: 1.8 parts by mass of phenolic antioxidant. Crosslinking agent: 0.2 parts by mass of isocyanate crosslinking agent.

[0073] preparation

[0074] S1: First, the twin-screw kneading machine is heated to 120° C., and then 40 parts by weight of 3L rubber with a Mooney value of 60 and 1.8 parts by weight of amine antioxidant are put into the twin-screw kneading machine for heating. When the EVA resin begins to soften, the screw kneading is performed, and the viscosity of the 3L rubber decreases and is melt-mixed with the EVA resin to form a first mixture.

[0075] S2: Continue to heat the twin-screw kneading machine to 170° C., add 20 parts by mass of rosin resin and 18 parts by mass of C5 petroleum resin to the first mixture in batches, and fully melt the tackifying resin and the first mixture to form a second mixture.

[0076] S3: 0.2 parts by mass of isocyanate crosslinking agent is diluted with 10 parts by mass of white oil and added to the second mixture in batches, and the crosslinking agent and the second mixture are fully melted to obtain hot melt adhesive.

[0077] The hot melt glue of Examples 1-5 and Comparative Examples 1-2 was coated on a 200um thick cloth substrate, and the amount of glue coated was 120g / ㎡. After rewinding and slitting, the samples of Examples 1-5 and Comparative Examples 1-2 were taken. The sample specifications were 25mm wide roll samples. The samples were placed in an environment of 23℃ / 55 humidity for one day and then tested. Another sample was taken, and the same sample was placed in a constant temperature box at 70℃ for 24h and then the same test was performed. The sample's holding force was tested according to GB / T 30776-2014. The test results are shown in Table 1 below.

[0078] Table 1 Test results of Examples 1-5 and Comparative Examples 1-2

[0079]

[0080] In summary, the natural rubber type hot melt adhesive of the present invention achieves a similar effect to that of a plasticizer by adding EVA to the front end of the kneaded natural rubber, greatly reducing the friction chain breaking effect of the rubber molecules during the kneading process, and better retaining the integrity of the natural rubber molecular chain. After pretreatment in this way, other components can be better blended with the natural rubber macromolecules, and the prepared natural rubber type hot melt adhesive is not easy to leave residual glue during the application process. In addition, the preparation method of the natural rubber type hot melt adhesive is simple, the preparation cost is low, and it is suitable for mass production.

[0081] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0082] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A natural rubber type hot melt adhesive, characterized in that: The invention comprises the following components according to weight percentage: 40%-60% natural rubber, 5%-15% EVA resin, 40%-60% tackifying resin, 5%-10% softener, 1%-2% antioxidant and 0.1%-0.2% crosslinking agent.

2. The natural rubber type hot melt adhesive according to claim 1, characterized in that: The natural rubber is selected from 3L rubber with a Mooney viscosity between 50 and 80, constant viscosity CV rubber and white wrinkle rubber.

3. The natural rubber type hot melt adhesive according to claim 1, characterized in that: The VA content of the EVA resin is between 10% and 25%.

4. The natural rubber type hot melt adhesive according to claim 1, characterized in that: The tackifying resin is selected from one or more of rosin resin, terephthalate resin and petroleum resin.

5. The natural rubber type hot melt adhesive according to claim 4, characterized in that: The petroleum resin is selected from one or more of C5 petroleum resin, C9 petroleum resin, C5-C9 copolymerized petroleum resin, styrene resin, dicyclopentadiene resin, pentaerythritol ester resin and hydrogenated resin.

6. The natural rubber type hot melt adhesive according to claim 1, characterized in that: The softener is selected from one of naphthenic oil, white oil and liquid polyisobutylene.

7. The natural rubber type hot melt adhesive according to claim 1, characterized in that: The antioxidant is selected from one or more of phenolic antioxidants, amine antioxidants, heterocyclic antioxidants, peroxide decomposition antioxidants and organophosphorus antioxidants.

8. The natural rubber type hot melt adhesive according to claim 1, characterized in that: The cross-linking agent is an isocyanate cross-linking agent.

9. A method for preparing natural rubber type hot melt adhesive, characterized in that: include: The twin-screw kneading machine is heated to 100-120° C., natural rubber, EVA resin and antioxidant are put into the machine for heating, and screw kneading is performed when the EVA resin begins to soften, and the viscosity of the natural rubber decreases and is melt-mixed with the EVA resin to form a first mixture; The twin-screw kneading machine is further heated to 150-170° C., tackifying resin is added to the first mixture in batches, and the tackifying resin and the first mixture are fully melted to form a second mixture; Diluting the crosslinking agent with a softener and adding the crosslinking agent to the second mixture in batches, and fully melting the crosslinking agent and the second mixture to obtain the natural rubber type hot melt adhesive; The invention comprises the following components according to weight percentage: 40%-60% natural rubber, 5%-15% EVA resin, 40%-60% tackifying resin, 5%-10% softener, 1%-2% antioxidant and 0.1%-0.2% crosslinking agent.

10. The method for preparing natural rubber type hot melt adhesive according to claim 9, characterized in that: The amount of the tackifying resin added to the first mixture each time is less than or equal to 20% of the total amount of the tackifying resin.

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