CN111410919A

CN111410919A - Protection film convenient to recycle

Info

Publication number: CN111410919A
Application number: CN202010404860.7A
Authority: CN
Inventors: 刘兵; 谢伟峡
Original assignee: Jiangxi Boc Technology Group Co ltd
Current assignee: Jiangxi Boc Technology Group Co ltd
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2020-07-14
Anticipated expiration: 2040-05-12
Also published as: CN111410919B

Abstract

The invention discloses a protective film convenient to recycle, and relates to the technical field of protective films. The protective film provided by the scheme sequentially comprises a base material layer, an adhesive layer and a release layer; the adhesive layer is prepared from modified rubber and polyaspartic acid resin urea according to the weight ratio of 1: 0.4-1. According to the invention, the polyaspartic acid resin urea and the modified rubber are selected to prepare the adhesive layer, the weather resistance is good, the yellowing resistance is more excellent than that of the traditional adhesive, and the polyolefin elastomer coating release film is combined, so that the protective film is more green and environment-friendly, direct mixing granulation during recovery is facilitated, pretreatment is not required, the difficulty of recovery processing is greatly reduced, and the recovery process is simple.

Description

Protection film convenient to recycle

Technical Field

The invention relates to the technical field of protective films, in particular to a protective film convenient to recycle.

Background

The protective film becomes a very important flexible packaging material and is widely applied to surface protection in the product transportation process and surface protection in the manufacturing process; die cutting protection, transfer pasting and protection of various metals, films and adhesive tapes; protecting the processing surfaces of various optical glasses; various plastic housings, keyboards and other plastic parts.

With the rapid development of plastic products, environmental protection problems have been raised, plastic wastes such as protective films and films seriously affect our living environment, and the plastic wastes are also named as white wastes and become one of the main pests harming the environment for nearly two decades!

In the increasingly important attention of people on the environmental protection problem, plastic products such as protective films and the like must be developed to green products, and the plastic products can be selected by direct users and indirect users only by walking a road which is pollution-free, easy to decompose and recyclable. In order to properly solve the problem of the film waste, researchers are changing the structure of the protective film itself so that the waste protective film is completely decomposed in a not too long time.

The environmental protection problem of the protective film is mainly solved by two modes of recovery and degradation. The recovery mode is mainly through modifying the material of the protective film, as patent CN106010343A discloses that the adhesive is recovered and utilized through modifying the adhesive into an aqueous system; the biodegradable protective film is prepared by adding a compatilizer to improve the compatibility between polylactic acid, polypropylene and polyethylene, so that the prepared polylactic acid/polypropylene/polyethylene base material layer has better processing performance and physical performance, and meanwhile, due to the existence of polylactic acid, the waste protective film can be biodegraded in the natural environment, thereby reducing the pollution to the environment.

However, the existing protective film is difficult to process and utilize again after being recycled due to poor composition compatibility of materials, and cannot achieve the effect of environmental protection.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a protective film which is convenient to recycle aiming at some defects mentioned in the background technology.

In order to solve the above problems, the present invention proposes the following technical solutions:

a protective film convenient for recycling comprises a substrate layer, an adhesive layer and a release layer in sequence; the adhesive layer is prepared from modified rubber and polyaspartic acid resin urea according to the weight ratio of 1: 0.4-1.

The further technical scheme is that the polyaspartic acid resin urea is prepared from a main agent and a curing agent according to the weight ratio of 1: 0.8-1.2; the main agent comprises the following components in parts by weight:

70-80 parts of polyaspartic acid resin; 1-5 parts of an absorbent; 8-12 parts of a molecular sieve; 0.1-0.5 part of defoaming agent; 0.1-0.5 part of wetting agent;

the curing agent is at least one of HDI tripolymer, IPDI prepolymer and modified IPDI curing agent.

The polyaspartic acid resin is further characterized in that the polyaspartic acid resin is one or more of N, N '- (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetraethyl ester, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetrabutyl ester, N '- (methylenebis- (1-methyl-4, 1-cyclohexanediyl)) tetraaspartic acid tetraethyl ester and N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraaspartic acid tetraethyl ester.

The further technical scheme is that the modified IPDI curing agent is prepared by reacting polyester polyol, polyether polyol and IPDI.

The further technical scheme is that the NCO content of the modified IPDI curing agent is 1-10%.

The further technical scheme is that the preparation process of the modified IPDI curing agent comprises the following steps: reacting polyester polyol, polyether polyol and IPDI at 50-70 ℃ for 4-6 hours, then heating to 90-95 ℃, reacting for 3-4 hours, cooling to 40-50 ℃, and measuring the content of NCO to be 1-10% to obtain the modified IPDI curing agent.

The further technical scheme is that the modified rubber is modified styrene-butadiene rubber and/or modified ethylene propylene rubber.

The modified styrene-butadiene rubber is thermoplastic styrene-butadiene rubber, preferably thermoplastic styrene-butadiene rubber with a star-shaped structure.

The modified ethylene propylene rubber is thermoplastic modified ethylene propylene rubber.

The further technical scheme is that the thickness of the adhesive layer is 5-50 um.

The further technical scheme is that the substrate layer is a PET film, a P L A film or a BOPP film.

Preferably, the substrate layer is a colorless transparent PET film, a colorless transparent P L A film or a colorless transparent BOPP film.

The further technical scheme is that the thickness of the base material layer is 10-100 um.

The further technical proposal is that the thickness of the release layer is 15-50 um.

The release layer is different from the traditional organic silicon release film and is a polyolefin elastomer coating release film so as to be recycled, the release force is 5-50 g/25mm, bubbles are easy to appear in the protective film in the bonding process due to too low release force, and the reusability of the protective film is greatly reduced due to too high release force. In a preferred embodiment, the release force of the polyolefin elastomer release film is 5-30 g/25mm, and the protective film is convenient to attach and can be repeatedly used for multiple times.

Compared with the prior art, the invention can achieve the following technical effects:

this scheme makes the adhesive layer through chooseing for use polyaspartic acid resin urea and modified rubber, contains polyaspartic acid resin in the adhesive, through arranging with the curing agent, make the weatherability of adhesive good, yellowing resistance can be more excellent than traditional adhesive, combine polyolefin elastomer coating from the type membrane, make the protection film more green, directly mix the granulation when being favorable to retrieving, and need not the preliminary treatment, greatly reduced the degree of difficulty of retrieving processing, retrieve simple process.

In addition, the adhesive prepared from the polyaspartic acid resin is innovatively applied to the protective film, the weather resistance and yellowing resistance of the protective film are improved by utilizing the weather resistance of the polyaspartic acid resin, the protective film can be directly granulated when being recovered, and the recovery cost is reduced.

Detailed Description

The technical solutions in the examples will be clearly and completely described below. It is apparent that the embodiments to be described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the embodiments of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention. As used in the description of embodiments of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The embodiment of the invention provides a protective film convenient to recycle, which sequentially comprises a substrate layer, an adhesive layer and a release layer; the adhesive layer is formed by modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.4-1.

The adhesive layer is prepared by drying an adhesive and modified rubber, wherein the adhesive is polyaspartic acid resin urea which contains polyaspartic acid ester, can react with isocyanate, can form a film at normal temperature, and has excellent weather resistance and yellowing resistance.

The adhesive is a general name of a large class of materials, and the adhesive in a certain specific application field must have corresponding performance characteristics and meet the requirement on environmental safety and recoverability, so the design requirement of people is met by adopting different types of resin raw material matching systems and adjusting different formula compositions. Specifically, the polyaspartic acid resin urea provided by the invention is prepared from a main agent and a curing agent according to the weight ratio of 1: 0.8-1.2; the main agent comprises the following components in parts by weight:

In a specific embodiment, the curing agent is a composition of an HDI trimer and a modified IPDI curing agent, wherein the mass ratio of the HDI trimer to the modified IPDI curing agent is 1-2: 3-6.

In a specific embodiment, the curing agent is a composition of an IPDI prepolymer and a modified IPDI curing agent, wherein the mass ratio of the IPDI prepolymer to the modified IPDI curing agent is 1-2: 3-6.

In a specific embodiment, the curing agent is a composition of an HDI trimer, an IPDI prepolymer and a modified IPDI curing agent, wherein the mass ratio of the HDI trimer to the IPDI prepolymer to the modified IPDI curing agent is 1-2: 1-2: 3-6.

In the polyaspartic acid resin urea provided by the invention, the main agent does not contain an organic solvent and a phthalate plasticizer, belongs to a solvent-free system, does not contain heavy metal, is green and environment-friendly, and is nontoxic and harmless; meanwhile, the adhesive also has good physical properties: the polyurethane adhesive has the advantages of good weather resistance, difficult color change, high tensile strength and elongation at break, good rebound resilience, easy construction, and excellent operability and physical properties which are equivalent to those of the conventional polyurethane adhesive, has excellent environmental protection safety and physical properties, is matched with modified rubber for use, and has high adhesive force and large viscosity.

Preferably, the polyaspartic acid resin is one or more of N, N '- (methylenebis-4, 1-cyclohexanediyl) tetraacetate, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartate, N '- (methylenebis- (1-methyl-4, 1-cyclohexanediyl)) tetraacetate, and N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraaspartate.

The low-viscosity aspartic resin N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraaspartic acid tetraethyl ester can reduce the viscosity of an adhesive system, ensure proper coating viscosity, avoid the use of organic solvents and phthalate plasticizers, and is safe and environment-friendly. In addition, the N, N' - (methylene di-4, 1-cyclohexanediyl) tetraacetylaspartate has higher reaction speed and better bonding strength, and the resin modified IPDI curing agent has lower reaction speed, is matched with HDI tripolymer for use, can flexibly control the reaction time, reduces the coating requirement and is convenient to operate.

The invention preferably uses the above-mentioned polyaspartic acid resins with different viscosities and flexibility in a mixed manner, the polyaspartic acid resin with high viscosity is complementary with the flexible polyaspartic acid resin, and the adhesive force and flexibility of the adhesive can be directionally adjusted by adjusting the proportion of the main agent and the curing agent, so that the adhesive force of the protective film is improved.

Preferably, the modified IPDI curing agent is prepared by reacting polyester polyol, polyether polyol and IPDI.

Preferably, the NCO content of the modified IPDI curing agent is 1-10%.

Preferably, the preparation process of the modified IPDI curing agent is as follows: reacting polyester polyol, polyether polyol and IPDI at 50-70 ℃ for 4-6 hours, then heating to 90-95 ℃, reacting for 3-4 hours, cooling to 40-50 ℃, and measuring the content of NCO to be 1-10% to obtain the modified IPDI curing agent.

The polyester polyols and polyether polyols are described in detail below:

polyester polyols

The molecular weight of polyester polyol in the modified IPDI curing agent is preferably within the range of 500-8000, the molecular weight is too low, excessive isocyanate is consumed, air bubbles are easily generated in the curing process, in addition, the adhesive layer is hard after curing, and the elongation at break is reduced. The molecular weight is too large, the viscosity of the adhesive is increased, the fluidity is reduced, and the NCO% content is reduced, so that the strength of the later-stage adhesive layer is influenced.

The polyester polyol in the modified IPDI curing agent can be prepared by esterification or ester exchange reaction of dihydric alcohol and dicarboxylic acid, anhydride or dicarboxylic ester.

The dihydric alcohol used in the preparation of the polyester polyol in the modified IPDI curing agent is selected from one or more of aliphatic dihydric alcohol and aromatic dihydric alcohol, and preferably the carbon atom number is 2-12; including but not limited to ethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 2-dimethyl-1, 3-propanediol (neopentyl glycol), 1, 4-cyclohexanedimethanol, 3-methyl-1, 5-pentanediol, 2, 4-diethyl-1, 5-pentanediol, 2, 4-trimethyl-1, 3-pentanediol, decanediol, and dodecanediol, more preferably one or more of neopentyl glycol, 3-methyl-1, 5-pentanediol, 2, 4-diethyl-1, 5-pentanediol, 2, 4-trimethyl-1, 3-pentanediol and the like, and the like.

The dicarboxylic acid, anhydride or dicarboxylic acid ester used in the preparation of the polyester polyol in the modified IPDI curing agent is one or more of aliphatic, alicyclic and aromatic dicarboxylic acid, anhydride or dicarboxylic acid ester, and the preferred carbon atom number is 4-15; including but not limited to one or more of phthalic acid, phthalic anhydride, dimethyl phthalate, dimethyl terephthalate, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, phthalic anhydride, and tetrahydrophthalic anhydride; more preferably one or more of adipic acid, sebacic acid, terephthalic acid, isophthalic acid.

The number average molecular weight of the polyester polyol in the modified IPDI curing agent is 500-8000, preferably 1000-6000, and more preferably 1500-3000.

Examples of the polyester polyol according to the present invention include, but are not limited to, adipic acid-based polyester glycol, aromatic polyester glycol, polycaprolactone glycol, and the like, and preferably, the polyester polyol includes one or more of PEA2000, PEA3000, PBA2000, PBA3000 of the new york institute chemical industry, ltd, or PH56, PD56 of the changxing chemical industry ltd, taiwan, or CMA-3044 (number average molecular weight 3000), CMA-44 (number average molecular weight 2000) N-112 (number average molecular weight 1000) of the wakame chemical industry ltd.

Polyether polyols

In the modified IPDI curing agent, the molecular weight of the polyether polyol is preferably within the range of 300-6000, the molecular weight is too low, excessive isocyanate is consumed, bubbles are easily generated in the curing process, in addition, the adhesive layer is hard after curing, and the elongation at break is reduced. The molecular weight is too large, the viscosity of the adhesive is increased, the fluidity is reduced, and the NCO% content is reduced, so that the strength of the later-stage adhesive layer is influenced.

Preferably, the epoxy compound used in the preparation of the polyether polyol is preferably one or more of ethylene oxide, propylene oxide and Tetrahydrofuran (THF).

Preferably, the polyether polyol in the modified IPDI curing agent of the invention comprises one or more of polyoxypropylene triol, polyoxypropylene diol, ethylene oxide-propylene oxide copolyether triol, tetrahydrofuran-propylene oxide copolyether diol.

The polyoxypropylene triol provided by the invention has the number average molecular weight of 300-3000, preferably 400-2000, more preferably 500-1000, and the initiator is preferably one or more of glycerol, trimethylolpropane and diethanolamine. Alternative examples include, but are not limited to, MN-500 (number average molecular weight 500), MN-1000 (number average molecular weight 1000), and the like, available from Dow chemical Co., Ltd.

The number average molecular weight of the polyoxypropylene glycol in the modified IPDI curing agent of the invention is 400-6000, preferably 600-3000, more preferably 1000-2000, the initiator is one or more of water, ethylene glycol and 1, 2-propylene glycol, and optional examples include, but are not limited to, Shandong Landong Daihang chemical industry, Inc. D L-1000 (number average molecular weight 1000), D L-2000 (number average molecular weight 2000), and the like.

The ethylene oxide-propylene oxide copolyether triol has the number average molecular weight of 1000-5000, preferably 1500-3500, more preferably 2000-3000, and the initiator is preferably glycerol or trimethylolpropane. Alternative examples include, but are not limited to, MN-3050 (number average molecular weight 3000) from Shandong Lanxingdong chemical Co., Ltd.

The tetrahydrofuran-propylene oxide copolyether glycol has the number average molecular weight of 1000-5000, preferably 1500-3500, more preferably 2000-3000, and the initiator is preferably one or more of water, ethylene glycol and 1, 2-propylene glycol. Alternative examples include, but are not limited to, DCB-2000 (number average molecular weight 2000), DCB-3000 (number average molecular weight 3000), available from Nissan oil Co., Ltd.

More preferably, the polyether polyol in the modified IPDI curing agent of the present invention comprises a mixture of polyoxypropylene triol and polyoxypropylene diol in a mass ratio of 1:0.1-3, preferably 1:0.2-2, more preferably 1: 0.5-1.

As another preferred technical scheme, the polyether polyol in the modified IPDI curing agent comprises a polyoxypropylene diol and a tetrahydrofuran-propylene oxide copolyether diol in a mass ratio of 1:0.1-4, preferably 1:0.2-2, more preferably 1: 0.5-1.

As another preferred technical scheme, the polyether polyol in the modified IPDI curing agent comprises polyoxypropylene triol and ethylene oxide-propylene oxide copolyether triol in a mass ratio of 1:0.1-4, preferably 1:0.2-2, more preferably 1: 0.5-1.

The low molecular weight polyether polyol in the modified IPDI curing agent has good diffusion performance, so that the polyaspartic acid resin urea adhesive obtained after the modified IPDI curing agent reacts with the main agent has good bonding performance; the water resistance of the modified IPDI curing agent is further improved by the long carbon chain structure in the medium molecular weight polyether chain, and due to the existence of the flexible chains, the polymer has better diffusion performance, so that the good bonding performance of the polyaspartic acid resin urea adhesive and a base material is further improved; the existence of the polar group of the polyester polyol increases the strength of the modified IPDI curing agent, and meanwhile, the existence of the side chain group protects the ester group from being hydrolyzed easily; the polyether polyol and the polyester polyol have the combined action, so that the adhesive has excellent durability, the bonding performance of the polyaspartic acid resin urea adhesive and a base material is also obviously improved, and the durability is improved. In addition, the polyaspartic acid resin urea adhesive obtained by matching the modified IPDI curing agent with the polyaspartic acid resin has excellent yellowing resistance, so that the prepared adhesive layer has high viscosity, high adhesive force and good yellowing resistance and weather resistance, the recovery process of the protective film is further simplified, the recovery cost is reduced, and the protective film is convenient to recover.

The modified IPDI curing agent is a hydroxyl modified curing agent, has high permeability and is non-toxic, and compared with a curing agent containing TDI and MDI, the curing agent provided by the invention avoids the volatilization toxicity of free TDI, and has higher safety.

Preferably, the modified rubber is modified styrene-butadiene rubber and/or modified ethylene-propylene rubber.

Preferably, the adhesive layer has a thickness of 5-50 um.

Preferably, the thickness of the substrate layer is 10-100 um.

Preferably, the thickness of the release layer is 15-50 um.

The release layer is a polyolefin elastomer coating release film, the release force is 5-50 g/25mm, bubbles are easy to appear in the protective film in the bonding process due to too low release force, and the reusability of the protective film is greatly reduced due to too high release force. In a preferred embodiment, the release force of the polyolefin elastomer coating release film is 5-30 g/25mm, and the protective film is convenient to adhere and can be repeatedly used for multiple times.

The following are specific examples:

example 1

The embodiment of the invention provides a protective film convenient to recycle, which sequentially comprises a substrate layer, an adhesive layer and a release layer.

The adhesive layer is prepared by mixing modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.5.

The thickness of the adhesive layer is 25 um.

The substrate layer is that PET film thickness is 40 um.

The thickness of the release layer is 15 um.

Wherein the polyaspartic acid resin urea adhesive is prepared from a main agent and a curing agent according to the weight ratio of 1: 1; the main agent comprises the following components in parts by weight:

40 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetraethyl ester; 30 parts of N, N' - (methylene bis- (1-methyl-4, 1-cyclohexanediyl)) tetraacetate; 2 parts of oxazolidine absorbent; 10.1 parts of A3 molecular sieve; 0.3 part of defoaming agent; 0.4 part of wetting agent; the curing agent is IPDI trimer.

The modified rubber is modified styrene-butadiene rubber.

The preparation method of the protective film convenient for recycling provided by the embodiment is as follows:

uniformly mixing the main agent and the curing agent in proportion to obtain the polyaspartic acid resin urea adhesive;

adding modified rubber into the polyaspartic acid resin urea adhesive, uniformly mixing, uniformly coating on a substrate layer, wherein the coating thickness is a preset thickness, and drying to obtain a substrate layer-adhesive layer;

and (3) compounding a release film on the substrate layer-adhesive layer to obtain the protective film convenient to recycle.

Example 2

The adhesive layer is prepared by mixing modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.8.

The thickness of the adhesive layer is 45 um.

The substrate layer is a BOPP film.

The thickness of the release layer is 25 um.

Wherein the polyaspartic acid resin urea adhesive is prepared from a main agent and a curing agent according to the weight ratio of 1: 0.9; the main agent comprises the following components in parts by weight:

20 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraacetate; 30 parts of N, N' - (methylene bis- (1-methyl-4, 1-cyclohexanediyl)) tetraacetate; 25 parts of N, N' - (poly (oxy (methyl-1, 2-ethylene) diyl) tetraacetyldiaspartate and 2 parts of oxazolidine absorbent; 8.5 parts of A3 molecular sieve; 0.4 part of defoaming agent; 0.5 part of wetting agent; the curing agent is a modified IPDI curing agent.

The NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 6.42% to obtain the modified IPDI curing agent.

The modified rubber is modified ethylene propylene rubber.

The preparation method of the protective film convenient for recycling provided by the embodiment is the same as that of the embodiment 1.

Example 3

The thickness of the adhesive layer is 10 um.

The substrate layer is BOPP film, thickness 30 um.

The thickness of the release layer is 16 um.

70 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraacetate; 2 parts of oxazolidine absorbent; 9 parts of A3 molecular sieve; 0.1 part of defoaming agent; 0.2 part of wetting agent; the curing agent is an IPDI prepolymer and a modified IPDI curing agent according to the mass ratio of 1: 3 to obtain the compound.

The NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 7.15% to obtain the modified IPDI curing agent.

The modified rubber is modified styrene-butadiene rubber.

Example 4

The adhesive layer is prepared by mixing modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.6.

The thickness of the adhesive layer is 25 um.

The substrate layer is BOPP film, thickness 48 um.

The thickness of the release layer is 25 um.

50 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraacetate; 25 parts of N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraacetyldiaspartate; 1.8 parts of oxazolidine absorbent; 11 parts of A3 molecular sieve; 0.3 part of defoaming agent; 0.2 part of wetting agent; the curing agent is composed of HDI tripolymer, IPDI and modified IPDI curing agent, and the weight ratio of the HDI tripolymer to the IPDI curing agent is 1: 2: 3.

the NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 4.35% to obtain the modified IPDI curing agent.

The modified rubber is modified styrene-butadiene rubber.

Example 5

The adhesive layer is prepared by mixing modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.4.

The thickness of the adhesive layer is 50 um.

The substrate layer is BOPP film, thickness 80 um.

The thickness of leaving the type layer is 45 um.

Wherein the polyaspartic acid resin urea adhesive is prepared from a main agent and a curing agent according to the weight ratio of 1: 1.1; the main agent comprises the following components in parts by weight:

50 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraacetate; 25 parts of N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraacetyldiaspartate; 1.8 parts of oxazolidine absorbent; 11 parts of A3 molecular sieve; 0.3 part of defoaming agent; 0.2 part of wetting agent; the curing agent is composed of HDI tripolymer, IPDI and modified IPDI curing agent, and the weight ratio of the HDI tripolymer to the IPDI curing agent is 1: 2: 5.

the NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 2.95% to obtain the modified IPDI curing agent.

The modified rubber is modified ethylene propylene rubber.

Example 6

The adhesive layer is prepared by mixing modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.7.

The thickness of the adhesive layer is 45 um.

The substrate layer is BOPP film, thickness 75 um.

The thickness of the release layer is 30 um.

40 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetraethyl ester; 30 parts of N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraacetyldiaspartate; 1.8 parts of oxazolidine absorbent; 12 parts of A3 molecular sieve; 0.3 part of defoaming agent; 0.2 part of wetting agent; the curing agent is composed of HDI tripolymer, IPDI and modified IPDI curing agent, and the weight ratio of the HDI tripolymer to the IPDI curing agent is 1: 2: 5.

the NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 5.5% to obtain the modified IPDI curing agent.

The modified rubber is modified ethylene propylene rubber.

Example 7

The thickness of the adhesive layer is 35 um.

The substrate layer is the PET film, thickness 45 um.

The thickness of the release layer is 15 um.

40 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetraethyl ester; 20 parts of N, N '- (polyoxy (methyl-1, 2-ethylidene) diyl) tetraacetyldiaspartate and 10 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraacetylaspartate; 1.8 parts of oxazolidine absorbent; 12 parts of A3 molecular sieve; 0.3 part of defoaming agent; 0.2 part of wetting agent; the curing agent is composed of HDI tripolymer, IPDI and modified IPDI curing agent, and the weight ratio of the HDI tripolymer to the IPDI curing agent is 1: 1: 6.

the NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 6.01% to obtain the modified IPDI curing agent.

The modified rubber is modified styrene-butadiene rubber.

Example 8

The adhesive layer is prepared by mixing modified rubber and polyaspartic acid resin urea adhesive according to the weight ratio of 1: 0.9.

The thickness of the adhesive layer is 40 um.

The substrate layer is the PET film, thickness 80 um.

The thickness of the release layer is 19 um.

40 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetraethyl ester; 20 parts of N, N '- (polyoxy (methyl-1, 2-ethylidene) diyl) tetraacetyldiaspartate and 10 parts of N, N' - (methylenebis-4, 1-cyclohexanediyl) tetraacetylaspartate; 1.8 parts of oxazolidine absorbent; 12 parts of A3 molecular sieve; 0.3 part of defoaming agent; 0.2 part of wetting agent; the curing agent is composed of HDI tripolymer, IPDI and modified IPDI curing agent, and the weight ratio of the HDI tripolymer to the IPDI curing agent is 1: 1: 3.

the NCO content of the modified IPDI curing agent is 1-10%. The preparation process of the modified IPDI curing agent comprises the following steps: and (2) reacting polyester polyol, polyether polyol and IPDI at 65 ℃ for 4 hours, then heating to 90 ℃, reacting for 4 hours, cooling to 50 ℃, and measuring the content of NCO to reduce to 5.34% to obtain the modified IPDI curing agent.

The modified rubber is modified styrene-butadiene rubber.

Comparative example 1

The difference from example 1 is that the adhesive used is a conventional adhesive and does not contain polyaspartic acid resin.

Comparative example 2

The difference from example 1 is that the adhesive used is a polyurethane adhesive and does not contain polyaspartic acid resin.

Comparative example 3

The difference from example 6 is that the NCO content of the modified IPDI curing agent in the adhesive used is 11.5%.

Comparative example 4

The difference from example 6 is that in the main agent of the adhesive, the resin is a meta-amine or polyether type aspartic polyurea resin.

Performance testing

The protective films provided in examples 1 to 6 and comparative examples 1 to 4 which were easy to recycle were subjected to a performance test,

the test method is as follows:

and (3) testing the peel strength: the test was carried out as described in standard GB 2792-1988.

And (3) permanent adhesion testing: and testing by using a holding adhesion tester.

Initial tack test: the test was carried out according to the method described in standard GB 4852-1984.

And (3) yellowing resistance test: the protective film is attached to the surfaces of a stainless steel plate and glass, and is placed in an oven to be heated for 72 hours at 90 ℃, whether the color of the protective film is yellowed or not is observed, and the protective film is divided into four grades according to the degree of yellowing, namely severe yellowing, slight yellowing and no yellowing.

Testing residual glue: and (3) attaching the protective film to the surfaces of the stainless steel plate and the glass, heating the stainless steel plate and the glass in an oven at 150 ℃ for 30min, cooling the stainless steel plate and the glass, peeling the protective film, and checking whether residual glue exists on the surfaces of the stainless steel plate and the glass.

The test results are obtained by averaging 10 groups of parallel samples, and the test results are shown in tables 1 and 2.

Table 1: test results of examples 1 to 5

Item	Example 1	Example 2	Example 3	Example 4	Example 5
						Peel strength (g/25mm)	91.2	90.8	90.9	89.5	89.5
Permanent adhesive force (min)	181.1	178.3	179.2	180.4	180.4
						Initial tack	16#	16#	16#	16#	16#
Yellowing resistance	No yellowing	No yellowing	No yellowing	No yellowing	No yellowing
						Residual glue	Qualified	Qualified	Qualified	Qualified	Qualified

Table 2: test results of example 6 and comparative examples 1 to 4

Item	Example 6	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4
						Peel strength (g/25mm)	91.2	70.5	91.2	91.5	89.5
Permanent adhesive force (min)	181.1	130.3	175.1	180.5	180.4
						Initial tack	16#	14#	16#	16#	15#
Yellowing resistance	No yellowing	Yellow stain	Yellow stain	No yellowing	Yellow stain
						Residual glue	Qualified	Qualified	Qualified	Fail to be qualified	Fail to be qualified

As can be seen from the results of tables 1 and 2, comparative example 1, which uses a conventional adhesive and does not contain polyaspartic acid resin, is reduced in peel strength, permanent adhesion, and yellowing resistance, and is difficult to recycle directly; the adhesive used in comparative example 2 is a polyurethane adhesive and does not contain polyaspartic acid resin, although the protective film of comparative example 2 has a certain peel strength and permanent adhesion due to the viscosity of polyurethane, the yellowing resistance is poor because of the absence of polyaspartic acid resin, and it is difficult to directly recycle; the NCO content of the modified IPDI curing agent in the adhesive used in the comparative example 3 is 11.5%, so that the protective film has overlarge viscosity, adhesive residue occurs, and the product quality is influenced; in the main agent of the adhesive used in comparative example 4, the resin is a bit-group amine or polyether type aspartic polyurea resin, and the bit-group amine, benzene ring and epoxy belong to non-aging-resistant group structures, and the introduction of the structures undoubtedly influences the yellowing property and aging resistance of the protective film.

In conclusion, the protective film convenient to recycle provided by the invention has the advantages that the adhesive layer is prepared by selecting the polyaspartic acid resin urea adhesive and the modified rubber, the yellowing resistance is excellent, and the recycling process is favorably reduced; the BOPP substrate is preferably used as the substrate, so that the recycling cost performance is high; the recycling granulation process has the advantages that the effect of repeated use can be directly achieved through a recycling granulation mode, additional processing is not needed, and the energy is saved and the environment is protected.

The polyaspartic acid resin urea adhesive provided by the invention does not contain organic solvents and phthalate plasticizers, is green, safe and nontoxic, and has the advantages of simple preparation method and mild reaction conditions.

Further, the adhesive prepared from the polyaspartic acid resin is innovatively applied to the protective film in the scheme so as to improve the weather resistance of the protective film, and the polyolefin elastomer coating release film is combined, so that the protective film can be directly granulated during recovery, and the recovery cost is reduced.

In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

While the invention has been described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The protective film convenient to recycle is characterized by sequentially comprising a substrate layer, an adhesive layer and a release layer; the adhesive layer is prepared from modified rubber and polyaspartic acid resin urea according to the weight ratio of 1: 0.4-1.

2. The protective film convenient for recycling according to claim 1, wherein the polyaspartic acid resin urea is prepared from a main agent and a curing agent in a weight ratio of 1: 0.8-1.2; the main agent comprises the following components in parts by weight:

3. The protective film according to claim 2, wherein the polyaspartic acid resin is one or more of N, N '- (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetraethyl ester, N' - (methylenebis-4, 1-cyclohexanediyl) tetraaspartic acid tetrabutyl ester, N '- (methylenebis- (1-methyl-4, 1-cyclohexanediyl)) tetraaspartic acid tetraethyl ester, and N, N' - (polyoxy (methyl-1, 2-ethylidene) diyl) tetraaspartic acid tetraethyl ester.

4. The protective film for easy recycling according to claim 3, wherein the modified IPDI curing agent is prepared by reacting polyester polyol, polyether polyol and IPDI.

5. The protective film for easy recycling according to claim 4, wherein the NCO content of the modified IPDI curing agent is 1-10%.

6. The protective film convenient for recycling according to claim 5, wherein the preparation process of the modified IPDI curing agent is as follows: reacting polyester polyol, polyether polyol and IPDI at 50-70 ℃ for 4-6 hours, then heating to 90-95 ℃, reacting for 3-4 hours, cooling to 40-50 ℃, and measuring the content of NCO to be 1-10% to obtain the modified IPDI curing agent.

7. The protective film convenient to recycle of claim 6, wherein the modified rubber is modified styrene-butadiene rubber and/or modified ethylene-propylene rubber.

8. The protective film for easy recycling according to claim 7, wherein the adhesive layer has a thickness of 5-50 um.

9. The protective film facilitating recycling according to claim 8, wherein the substrate layer is a PET film, a P L a film, or a BOPP film.

10. The protective film convenient for recycling according to claim 9, wherein the thickness of the substrate layer is 10-100 um.