Acrylate emulsion for heat-sealing paper and preparation method thereof

Abstract

The invention discloses an acrylic emulsion for heat-sealing paper and a preparation method thereof, and relates to the technical field of emulsions. The emulsion comprises, by weight, 95-110 parts of deionized water, 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomers, 1-2 parts of hydroxyl functional monomers, 0.5-1 part of cross-linking monomers, 3-5 parts of long-chain esters of acrylic acid monomers, 2-4 parts of wax emulsions, 1.5-2.5 parts of emulsifiers, and 1-2 parts of initiators. The emulsion can improve the anti-rebound effect of the film layer after film formation by adding long-chain esters of acrylic acid monomers and wax emulsions; by adjusting the component ratio, the glass transition temperature of the emulsion can be made 25°C-35°C, with a dense film-forming effect, no powdering, and no rebound.

Description

Technical Field

[0001] The invention relates to the technical field of emulsions, and in particular to an acrylic ester emulsion for heat-sealing paper and a preparation method thereof. Background Art

[0002] PE coated paper has excellent water resistance, toughness, moisture barrier and low processing cost, and is widely used in the field of disposable food packaging. However, since PE film is non-degradable and non-recyclable, a large amount of discarded PE coated paper causes white pollution, which obviously does not meet the country's requirements for green environmental protection and sustainable development. At the same time, the regulations and policies of the plastic restriction order have prompted all walks of life to find solutions to reduce and replace plastic.

[0003] Acrylic emulsion technology is mature, the market volume is large, and acrylic emulsion has excellent film-forming properties, water resistance and repulpable recycling properties, so it has become the direction of environmentally friendly water-based coatings for coated paper, used to replace PE coating. The use of acrylic emulsion coated on the surface of paper can also give the paper protective properties, achieve a water barrier effect, and protect the paper from damage. For example, the Chinese invention patent with patent application number CN202311705368.3 discloses an acrylic emulsion for coating food packaging paper and a preparation method thereof. The acrylic emulsion for coating food packaging paper uses butyl acrylate and isooctyl acrylate as soft monomers, styrene and methyl methacrylate as hard monomers to prepare an emulsion with a glass transition temperature of 15 to 20°C. The paper using the emulsion is not easy to stick to the roller and does not fall off. However, since acrylic polymers are thermoplastic polymers, when the heating temperature gradually rises, the paint film gradually becomes soft and sticky, and the paper is easy to stick when it is rolled up (60°C), resulting in damage to the paper when it is unfolded and cannot be used normally. To solve this problem, the prior art uses a compounded hard acrylic emulsion with a high glass transition temperature to improve the adhesion problem, but this method will affect the decline of heat sealing performance. In addition, there is also the use of EAA emulsion instead of acrylic emulsion for coating. Although it has excellent anti-adhesive properties and good heat sealing properties, the preparation of EAA emulsion requires a high-pressure and high-temperature reaction process, and the product cost is expensive, resulting in low competitiveness. Therefore, developing an acrylic emulsion for heat-sealing paper, which can easily heat-seal the paper after coating at high temperatures and meet the requirements of anti-adhesion when the paper is rolled and stored, is a major problem of acrylic emulsion at present.

[0004] It can be seen that the existing technology still needs to be improved and enhanced. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an acrylic ester emulsion for heat-sealing paper and a preparation method thereof, aiming to solve the defect that the existing acrylic ester emulsion for heat-sealing paper is easy to stick when winding.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An acrylic ester emulsion for heat-sealing paper, wherein the emulsion comprises, by weight: 95-110 parts of deionized water, 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomers, 1-2 parts of hydroxyl functional monomers, 0.5-1 part of cross-linking monomers, 3-5 parts of long-chain esters of acrylic acid monomers, 2-4 parts of wax emulsions, 1.5-2.5 parts of emulsifiers, and 1-2 parts of initiators.

[0008] In the acrylic ester emulsion for heat-sealing paper, the long-chain ester of acrylic acid monomer is selected from a combination of one or more of lauryl acrylate, lauryl methacrylate, octadecyl acrylate and octadecyl methacrylate.

[0009] In the acrylic ester emulsion for heat-sealing paper, the emulsifier consists of an anionic emulsifier and a reactive anionic emulsifier.

[0010] In the acrylic ester emulsion for heat-sealing paper, the mass ratio of the anionic emulsifier to the reactive anionic emulsifier is 1:(0.3-0.6).

[0011] In the acrylic emulsion for heat-sealing paper, the reactive anionic emulsifier is selected from at least one of sodium acrylamide-2-methylpropane sulfonate, sodium allyloxyhydroxysulfonate, and emulsifiers of model SR-10 or SE-10 provided by Aidico.

[0012] In the acrylic emulsion for heat-sealing paper, the wax emulsion is the wax emulsion with model TL-204E-4 / V816E provided by Yijiu Chemical Company or / and the wax emulsion with model OE-6112B / O3-6303 provided by Tianshi Company.

[0013] In the acrylic ester emulsion for heat-sealing paper, the cross-linking monomer is selected from at least one of vinyl trimethoxysilane, glycidyl methacrylate, isobornyl methacrylate and trimethylolpropane trimethacrylate.

[0014] In the acrylic ester emulsion for heat-sealing paper, the carboxyl functional monomer is selected from a combination of one or more of acrylic acid, itaconic acid, maleic acid and maleic anhydride.

[0015] In the acrylic ester emulsion for heat-sealing paper, the hydroxyl functional monomer is selected from a combination of one or more of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate.

[0016] A method for preparing an acrylic emulsion for heat-sealing paper, which is used to prepare the emulsion as described above, and the method comprises the steps of:

[0017] a. Preparation of the bottom liquid A: 60 to 68 parts of deionized water and 0.7 to 2.2 parts of an emulsifier were added to a polymerization reactor, and the temperature was raised to 80 to 90 ° C in the reactor to obtain a bottom liquid A;

[0018] b. Preparation of pre-emulsion B: Add 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomer, 1-2 parts of hydroxyl functional monomer, 0.5-1 part of cross-linking monomer, 2-4 parts of wax emulsion, 22-26 parts of deionized water, and 0.3-0.8 parts of emulsifier into a pre-emulsification tank, stir and mix to form a uniform pre-emulsion to obtain pre-emulsion B;

[0019] c. Preparation of initiator solution C: Add 1 to 2 parts of initiator and 13 to 16 parts of deionized water to the initiator tank and mix well to obtain initiator solution C;

[0020] d. Add 3% to 6% of pre-emulsion B and 10% to 20% of initiator solution C to the polymerization reactor, stir at 80 to 90 ° C for 10 to 30 minutes, and then add the remaining pre-emulsion B and initiator solution C dropwise at a constant flow, and the addition time is controlled at 180 to 220 minutes;

[0021] e. When the amount of pre-emulsion B remains at 30% to 40%, stop adding pre-emulsion B and initiator solution C, add 3 to 5 parts of acrylic acid monomer long-chain ester to the remaining pre-emulsion B, mix well, and resume adding the remaining pre-emulsion B and initiator solution C;

[0022] f. After the addition is complete, keep warm at 80-90°C for 1-2 hours;

[0023] g. Cool down to 40-50°C, add defoamer and bactericide to the reaction kettle, stir for 0.5-1h, filter the material to obtain acrylic emulsion for heat sealing paper.

[0024] Beneficial effects:

[0025] The present invention provides an acrylic ester emulsion for heat-sealing paper and a preparation method thereof. The emulsion can improve the anti-sticking effect of the film layer after film formation by adding acrylic acid monomer long-chain ester and wax emulsion, especially acrylic acid monomer long-chain ester, which can form crystals on the surface of the film layer when the emulsion is film-formed. Since the crystals are acrylic acid monomer long-chain ester grafted on the outer layer crystals of the polymer, the chain segments are not easy to bend and soften, so that the product can maintain rigidity and non-stick at a winding temperature of 60°C, thereby playing an anti-sticking effect; secondly, the emulsion also uses carboxyl and hydroxyl hydrophilic monomers as The protective system of stable latex particles can enable the emulsion to quickly penetrate the fibers when coating paper, while improving the density and water resistance of the fibers, and reducing the problem of product stickiness during heating (60°C) during winding. Furthermore, the emulsion is compounded with soft monomers such as butyl acrylate, isooctyl acrylate and styrene to achieve a glass transition temperature of 25°C-35°C. The glass transition temperature can make the emulsion have high film density and good film-forming effect, which can improve the water and oil barrier properties of the paper on the one hand, and prevent the paper from losing powder when cut into rolls on the other hand. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention provides a flow chart of a method for preparing an acrylic emulsion for heat-sealing paper. DETAILED DESCRIPTION

[0027] The present invention provides an acrylic emulsion for heat-sealing paper and a preparation method thereof. To make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the following examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] The invention provides an acrylic ester emulsion for heat-sealing paper. The emulsion comprises, by weight, 95-110 parts of deionized water, 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomers, 1-2 parts of hydroxyl functional monomers, 0.5-1 part of cross-linking monomers, 3-5 parts of long-chain esters of acrylic acid monomers, 2-4 parts of wax emulsions, 1.5-2.5 parts of emulsifiers, and 1-2 parts of initiators.

[0029] The emulsion improves the anti-adhesion effect of the film layer after film formation by adding long-chain esters of acrylic acid monomers and wax emulsions, especially long-chain esters of acrylic acid monomers, which can form crystals on the surface of the film layer when the emulsion is formed. Since the crystals are long-chain esters of acrylic acid monomers grafted onto the outer layer of polymers, the chain segments are not easy to bend and soften, so that the product can maintain rigidity and non-adhesion at a winding temperature of 60°C, playing an anti-adhesion role; secondly, the emulsion also uses carboxyl and hydroxyl hydrophilic monomers as a protective system for stabilizing latex particles, which can promote The emulsion can quickly penetrate the fiber when coating paper, and while improving the density and water resistance of the fiber, it can reduce the problem of product sticking back when heated (60°C) during winding; furthermore, the emulsion is compounded with soft monomers butyl acrylate, isooctyl acrylate, and styrene to make the glass transition temperature of the emulsion 25°C-35°C. The glass transition temperature can make the film-forming density of the emulsion high and the film-forming effect good, which, on the one hand, makes the water and oil barrier properties of the paper good, and on the other hand, the paper is not easy to fall off when cut into rolls.

[0030] Since the glass transition temperature of the emulsion will affect the film-forming conditions and effects of the emulsion, if the glass transition temperature is too low, the emulsion will easily become sticky at room temperature after film formation, which is not suitable for paper stacking and anti-sticking; while if the glass transition temperature is too high, the emulsion film-forming conditions will be improved, and the paper will become brittle after film formation, which is not conducive to the use and heat sealing of the paper. In this regard, in the aforementioned emulsion, by adjusting the ratio of each component, an emulsion with a glass transition temperature of 25-35°C is obtained. Under the condition of having a good film-forming effect, the film layer is not easy to become sticky, and the use and heat sealing effects of the paper are good.

[0031] In a preferred embodiment, the long-chain ester of acrylic acid monomer is selected from a combination of one or more of lauryl acrylate, lauryl methacrylate, octadecyl acrylate, and octadecyl methacrylate. These long-chain esters of acrylic acid monomer have relatively long molecular chains, and thus are easy to form crystals on the surface of the film layer during the emulsion film formation process, thereby solving the problem of the film layer sticking back under heating conditions during winding.

[0032] Since the emulsifier affects the emulsification effect of the system and the progress of the emulsion polymerization reaction, in addition, since the wax emulsion is added to the emulsion components, anions are required to fully disperse it. Therefore, in a preferred embodiment, the emulsifier is compounded by anionic emulsifiers and reactive anionic emulsifiers, which has a better emulsification effect. Among them, the reactive anionic emulsifier is selected from at least one of sodium acrylamide-2-methylpropane sulfonate, sodium allyloxyhydroxysulfonate, and emulsifiers of model SR-10 or SE-10 provided by Aidico, but is not limited to the aforementioned types, and can also be other anionic emulsifiers with the same effect. The anionic emulsifier is at least one of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and disodium sulfosuccinate ethoxylated alcohol half ester.

[0033] In a more preferred embodiment, the mass ratio of the anionic emulsifier to the reactive anionic emulsifier is 1:(0.3-0.6). The anionic emulsifier and the reactive anionic emulsifier in this ratio are used together to have a better emulsification effect and can ensure the smooth progress of the emulsion polymerization.

[0034] In a preferred embodiment, the wax emulsion is selected from one or a combination of the wax emulsion model TL-204E-4 / V816E provided by Yijiu Chemical and the wax emulsion model OE-6112B / O3-6303 provided by Tianshi, which has better water and oil blocking effects.

[0035] Specifically, the crosslinking monomer is selected from at least one of vinyl trimethoxysilane, glycidyl methacrylate, isobornyl methacrylate, and trimethylolpropane trimethacrylate, but is not limited to the aforementioned crosslinking monomers. The aforementioned crosslinking monomers have extremely strong crosslinking properties, which can optimize the obtained acrylic emulsion from linear properties to network structure properties, improve the water and oil resistance of paper, and the polymer chain segments are not easy to re-stick when heated at a temperature of 60°C, and do not stick when rolled and squeezed.

[0036] The carboxyl functional monomer is selected from one or more combinations of acrylic acid, itaconic acid, maleic acid, and maleic anhydride.

[0037] The hydroxyl functional monomer is selected from one or more combinations of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate.

[0038] The initiator is one of ammonium persulfate and sodium persulfate or a mixture of two or more of them in any proportion.

[0039] The second aspect of the present invention also provides a method for preparing an acrylic emulsion for heat sealing paper, such as Figure 1 As shown, the method comprises the steps of:

[0040] a. Preparation of the bottom liquid A: 60 to 68 parts of deionized water and 0.7 to 2.2 parts of an emulsifier were added to a polymerization reactor, and the temperature was raised to 80 to 90 ° C in the reactor to obtain a bottom liquid A;

[0041] b. Preparation of pre-emulsion B: Add 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomer, 1-2 parts of hydroxyl functional monomer, 0.5-1 part of cross-linking monomer, 2-4 parts of wax emulsion, 22-26 parts of deionized water, and 0.3-0.8 parts of emulsifier into a pre-emulsification tank, stir and mix to form a uniform pre-emulsion to obtain pre-emulsion B;

[0042] c. Preparation of initiator solution C: Add 1 to 2 parts of initiator and 13 to 16 parts of deionized water to the initiator tank and mix well to obtain initiator solution C;

[0043] d. Add 3% to 6% of pre-emulsion B and 10% to 20% of initiator solution C to the polymerization reactor, stir at 80 to 90°C for 10 to 30 minutes, and then drip the remaining pre-emulsion B and initiator solution C at a constant flow rate, and control the dripping time to 180 to 220 minutes;

[0044] e. When the total amount of pre-emulsion B remains at 30% to 40%, stop adding pre-emulsion B and initiator solution C, add 3 to 5 parts of acrylic acid monomer long-chain ester to the remaining pre-emulsion B, mix well, and resume adding the remaining pre-emulsion B and initiator solution C;

[0045] f. After the addition is complete, keep warm at 80-90°C for 1-2 hours;

[0046] g. Cool down to 40-50°C, add defoamer and bactericide to the reaction kettle, stir for 0.5-1h, filter the material to obtain acrylic emulsion for heat sealing paper.

[0047] In the preparation method, by using raw materials with special component ratios, and in the preparation process, a seed pre-emulsification semi-continuous dripping process is adopted, so that the reaction in the polymerization system can be fully and stably carried out, and the gel rate is low. In addition, the long-chain ester of acrylic acid monomer is added in the second half of the polymerization reaction, so that the long-chain ester of acrylic acid monomer can be located in the outer layer, so that when the emulsion is formed into a film, the long-chain ester of acrylic acid monomer can be better crystallized, solving the problem of film layer re-adhesion; in addition, through the preparation step of pre-emulsion liquid B, the wax emulsion is fully mixed with the monomer under the action of anions, and the wax emulsion is uniformly distributed in the polymer latex particles in the emulsion, so that when the emulsion is coated on paper, the wax emulsion can be evenly distributed on the surface of the film layer, reducing the surface tension of the film layer, improving the water and oil resistance of the film layer, and improving the problem of film layer rolling adhesion.

[0048] To further illustrate the acrylic emulsion for heat-sealing paper and the preparation method thereof provided by the present invention, the following examples are provided.

[0049] Example 1

[0050] The invention discloses an acrylic ester emulsion for heat-sealing paper, wherein the raw materials thereof are composed of the following components in parts by weight: 95 parts of deionized water; 22 parts of butyl acrylate; 3 parts of isooctyl acrylate; 37 parts of styrene; 2 parts of carboxyl functional monomer; 1 part of hydroxyl functional monomer, 0.5 part of cross-linking monomer; 5 parts of long-chain ester of acrylic acid monomer; 2 parts of wax emulsion; 1.5 parts of emulsifier; and 1 part of initiator.

[0051] The preparation method of the acrylic ester emulsion for heat-sealing paper comprises the following steps:

[0052] Preparation of bottom liquid A: Add 57 parts of deionized water and 1 part of emulsifier into a polymerization kettle equipped with a stirrer, a condenser, and a constant flow pump feeding device, and heat the kettle until the temperature reaches 82°C;

[0053] Preparation of pre-emulsion B: add 22 parts of butyl acrylate, 3 parts of isooctyl acrylate, 37 parts of styrene, 2 parts of carboxyl functional monomer, 1 part of hydroxyl functional monomer, 0.5 parts of cross-linking monomer, 3 parts of wax emulsion, 23 parts of deionized water and 0.5 parts of emulsifier into a pre-emulsification tank with a monomer metering tank and a stirrer at room temperature and pressure, stir and mix into a uniform pre-emulsion, and stir for 30 minutes for use;

[0054] Preparation of initiator solution C: Add 1 part of initiator and 15 parts of deionized water to an initiator tank equipped with a stirrer and a constant flow dripping device at room temperature and pressure to prepare a uniform dilution solution;

[0055] When the temperature in the polymerization kettle reaches 82°C, 3% of the total amount of pre-emulsion B and 10% of the total amount of initiator solution C are added into the kettle. After 15 minutes, the remaining pre-emulsion B and initiator solution C are simultaneously added dropwise into the polymerization kettle through a constant flow pump feeding device and a constant flow dripping metering device. The dripping time is controlled within 180 minutes.

[0056] When the total amount of pre-emulsion B remains at 35%, the addition of pre-emulsion B and initiator solution C is stopped, 5 parts of acrylic acid monomer long-chain ester are added to the cylinder of pre-emulsion B, dispersed and stirred for 10 minutes, and then the addition of the remaining pre-emulsion B and initiator solution C is resumed;

[0057] After the addition was completed, the temperature in the polymerization reactor was controlled at 82°C and kept warm for 1 hour;

[0058] The temperature was lowered to 40° C., a defoamer and a bactericide were added to the reaction kettle, the mixture was stirred for 1 hour, and the material was filtered to obtain an acrylic emulsion for heat-sealing paper.

[0059] Example 2

[0060] The invention discloses an acrylic ester emulsion for heat-sealing paper, wherein the raw materials thereof include the following components in parts by weight: 105 parts of deionized water; 26 parts of butyl acrylate; 5 parts of isooctyl acrylate; 40 parts of styrene; 3 parts of carboxyl functional monomer; 1.5 parts of hydroxyl functional monomer, 1 part of cross-linking monomer; 4 parts of long-chain ester of acrylic acid monomer; 3 parts of wax emulsion; 2 parts of emulsifier; and 1.5 parts of initiator.

[0061] The preparation method of the acrylic ester emulsion for heat-sealing paper comprises the following steps:

[0062] Preparation of bottom material liquid A: add 65 parts of deionized water and 1.5 parts of emulsifier into a polymerization kettle equipped with a stirrer, a condenser and a constant flow pump feeding device, and heat the kettle until the temperature reaches 85°C;

[0063] Preparation of pre-emulsion B: add 26 parts of butyl acrylate, 5 parts of isooctyl acrylate, 40 parts of styrene, 3 parts of carboxyl functional monomer, 1.5 parts of hydroxyl functional monomer, 1 part of cross-linking monomer, 3 parts of wax emulsion, 0.5 parts of emulsifier and 24 parts of deionized water into a pre-emulsification tank with a monomer metering tank and a stirrer at room temperature and pressure, stir and mix into a uniform pre-emulsion, and stir for 40 minutes for standby use;

[0064] Preparation of initiator solution C: Add 2 parts of initiator and 16 parts of deionized water to an initiator tank equipped with a stirrer and a constant flow dripping device at room temperature and pressure to prepare a uniform dilution solution;

[0065] When the temperature in the polymerization kettle reaches 85°C, 4% of the total amount of pre-emulsion B and 15% of the total amount of initiator solution C are added into the kettle. After 20 minutes, the remaining pre-emulsion B and initiator solution C are simultaneously added dropwise into the polymerization kettle through a constant flow pump feeding device and a constant flow dripping metering device. The dripping time is controlled within 200 minutes.

[0066] When the total amount of pre-emulsion B remains at 35%, the addition of pre-emulsion B and initiator solution C is stopped, 4 parts of acrylic acid monomer long-chain ester are added to the cylinder of pre-emulsion B, dispersed and stirred for 10 minutes, and then the addition of the remaining pre-emulsion B and initiator solution C is resumed;

[0067] After the addition was completed, the temperature in the polymerization kettle was controlled at 85°C and kept warm for 1.5 hours;

[0068] The temperature was lowered to 45° C., a defoamer and a bactericide were added to the reaction kettle, the mixture was stirred for 1 hour, and the material was filtered to obtain an acrylic emulsion for heat-sealing paper.

[0069] Example 3

[0070] The invention discloses an acrylic ester emulsion for heat-sealing paper, wherein the raw materials thereof include the following components in parts by weight: 110 parts of deionized water; 28 parts of butyl acrylate; 6 parts of isooctyl acrylate; 45 parts of styrene; 4 parts of carboxyl functional monomer; 2 parts of hydroxyl functional monomer, 1 part of cross-linking monomer; 3 parts of long-chain ester of acrylic acid monomer; 4 parts of wax emulsion; 2.5 parts of emulsifier; and 2 parts of initiator.

[0071] The preparation method of the acrylic ester emulsion for heat-sealing paper comprises the following steps:

[0072] Preparation of bottom liquid A: Add 68 parts of deionized water and 2 parts of emulsifier into a polymerization kettle equipped with a stirrer, a condenser, and a constant flow pump feeding device, and heat the kettle until the temperature reaches 90°C;

[0073] Preparation of pre-emulsion B: add 27 parts of butyl acrylate, 6 parts of isooctyl acrylate, 45 parts of styrene, 4 parts of carboxyl functional monomer, 2 parts of hydroxyl functional monomer, 1 part of cross-linking monomer, 4 parts of wax emulsion, 26 parts of deionized water and 0.5 parts of emulsifier into a pre-emulsification tank with a monomer metering tank and a stirrer at room temperature and pressure, stir and mix to form a uniform pre-emulsion, and stir for 50 minutes for standby use;

[0074] Preparation of initiator solution C: Add 2 parts of initiator and 16 parts of deionized water to an initiator tank equipped with a stirrer and a constant flow dripping device at room temperature and pressure to prepare a uniform dilution solution;

[0075] When the temperature in the polymerization kettle reaches 90°C, 6% of the total amount of pre-emulsion B and 20% of the total amount of initiator solution C are added into the kettle. After 30 minutes, the remaining pre-emulsion B and initiator solution C are simultaneously added dropwise into the polymerization kettle through a constant flow pump feeding device and a constant flow dripping metering device. The dripping time is controlled at 220 minutes.

[0076] When the total amount of pre-emulsion B remains at 40%, the addition of pre-emulsion B and initiator solution C is stopped, 3 parts of acrylic acid monomer long-chain ester are added to the cylinder of pre-emulsion B, dispersed and stirred for 15 minutes, and then the addition of the remaining pre-emulsion B and initiator solution C is resumed;

[0077] After the addition was completed, the temperature in the polymerization kettle was controlled at 90°C and kept warm for 2 hours;

[0078] The temperature was lowered to 50° C., a defoamer and a bactericide were added to the reaction kettle, the mixture was stirred for 1 hour, and the material was filtered to obtain an acrylic emulsion for heat-sealing paper.

[0079] Comparative Example 1

[0080] An acrylic ester emulsion for heat-sealing paper, whose raw material composition and preparation method are basically the same as those of Example 2, except that: no long-chain ester of acrylic acid monomer is added, and the preparation steps related to the long-chain ester of acrylic acid monomer are omitted.

[0081] Comparative Example 2

[0082] An acrylic ester emulsion for heat-sealing paper, whose raw material composition and preparation method are basically the same as those of Example 2, except that: no wax emulsion is added, and the preparation steps related to the wax emulsion are omitted.

[0083] Comparative Example 3

[0084] An acrylic ester emulsion for heat-sealing paper, whose raw material composition and preparation method are basically the same as those of Example 2, except that: no long-chain ester of acrylic acid monomer and wax emulsion are added, and the preparation steps related to long-chain ester of acrylic acid monomer and wax emulsion are omitted or no corresponding components are added.

[0085] Comparative Example 4

[0086] An acrylic ester emulsion for heat-sealing paper, whose raw material composition and preparation method are basically the same as those of Example 2, except that: the long-chain ester of acrylic acid monomer is added when preparing pre-emulsion B.

[0087] The acrylic emulsion prepared above was applied on A4 kraft paper with a specification of 80 grams to prepare a dry weight of 8-10 g / m 2 Barrier test paper. Perform the following tests:

[0088] 1. Test the performance of acrylic emulsion according to GB / T 20623-2006 standard;

[0089] 2. Cobb value test: Use Cobb water absorption tester to measure the surface water absorption capacity of packaging materials. The test time is 30 minutes.

[0090] 3. Oil resistance test: The oil resistance grade determination method adopts TAPPI T 559cm-12 standard, which is: castor oil, toluene and n-heptane are used to prepare 12 test liquids (coded with 1-12 numbers) in different proportions, and then these 12 different test liquids are used to determine the oil and fat resistance of food packaging paper.

[0091] 4. Recycling performance test: The paper-based materials were pulverized by a hydraulic pulper for 5 min (4% pulp concentration, pulverization speed 3000 rpm), and then passed through a 0.15 mm slit screen for hand-sheeting. The paper recycling ratio (calculated as: paper fiber recovery rate = absolute dry weight of pulp after screening / absolute dry weight of pulp before screening * 100%) and the uniformity of the paper surface after recycling were evaluated.

[0092] 5. Heat sealing performance test: Take a piece of paper-based material prepared according to the above method, cut it into strips with a width greater than 15mm, adjust the heat sealing temperature on the heat sealer to 160℃ (single-layer hot pressing), the heat sealing pressure to 30KPa, and the heat sealing time to 1s. After the heat sealing is completed, cut the sample into a sample with a width of 15mm for standby use. After the obtained sample is stabilized at room temperature for 2 hours, use a tensile testing machine to test the heat sealing strength. When the strength of the seal and back seal is greater than 3N / 15mm and the base paper material is required to be broken, the heat sealing requirements of the heat sealing barrier coating can be met.

[0093] 6. Anti-adhesion test: Cut the coated paper-based material into square pieces of 5 cm in length and width, stack them together with the coating facing the coating side (face to face) and the back of the paper facing the coating side (back to back), press them with a 1 kg weight, put them in a 60°C oven and bake for 24 hours. After cooling, the face-to-face and back-to-back sides can be separated without pressure, which can meet the anti-heat adhesion requirements of the barrier coating.

[0094] 7. Glass transition temperature: Differential scanning calorimetry (DSC) is used to detect the product TG.

[0095] The performance test was carried out according to the above standards, and the test results are shown in Table 1 and Table 2 below:

[0096] Table 1. Performance test results of the embodiments

[0097]

[0098]

[0099] Table 2. Performance test results of comparative examples

[0100]

[0101]

[0102] As shown in Table 1, the emulsion performance of the acrylic emulsion for heat-sealing paper described in Examples 1-3 is good, and the various performance indicators measured after being coated on paper are also good, among which the COBB value is less than or equal to 2.2 g / m 2 The oil-proof grade is above grade 10, the surface is dense, which can reduce water absorption and improve oil-proof performance; at the same time, the face-to-face anti-adhesion and face-to-back anti-adhesion tests can be separated without pressure, and the surface is made of the heat-sealed acrylic emulsion described in this application, which has good anti-adhesion performance and can avoid adhesion during winding.

[0103] However, the face-to-face anti-adhesion properties of Comparative Documents 1-4 cannot be separated, and forcibly pulling them apart will cause the paper to break, indicating that the anti-adhesion properties of the emulsion cannot be improved when long-chain acrylic acid monomer esters and wax emulsions are not added to the emulsion, or when long-chain acrylic acid monomer esters are added too early.

[0104] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. An acrylic emulsion for heat sealing paper, characterized in that: The emulsion comprises, by weight: 95-110 parts of deionized water, 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomer, 1-2 parts of hydroxyl functional monomer, 0.5-1 part of cross-linking monomer, 3-5 parts of long-chain ester of acrylic acid monomer, 2-4 parts of wax emulsion, 1.5-2.5 parts of emulsifier and 1-2 parts of initiator.

2. The acrylic emulsion for heat sealing paper according to claim 1, characterized in that: The long-chain acrylic acid monomer ester is selected from the group consisting of lauryl acrylate, lauryl methacrylate, octadecyl acrylate, and octadecyl methacrylate, or a combination of one or more thereof.

3. The acrylic emulsion for heat sealing paper according to claim 1, characterized in that: The emulsifier consists of anionic emulsifier and reactive anionic emulsifier.

4. The acrylic emulsion for heat sealing paper according to claim 3, characterized in that: The mass ratio of the anionic emulsifier to the reactive anionic emulsifier is 1:(0.3-0.6).

5. The acrylic emulsion for heat sealing paper according to claim 3, characterized in that: The reactive anionic emulsifier is selected from at least one of sodium acrylamide-2-methylpropane sulfonate, sodium allyloxyhydroxysulfonate, and emulsifiers of model SR-10 or SE-10 provided by Aidico.

6. The acrylic emulsion for heat sealing paper according to claim 1, characterized in that: The wax emulsion is a wax emulsion of model TL-204E-4 / V816E provided by Yijiu Chemical Company or / and a wax emulsion of model OE-6112B / O3-6303 provided by Tianshi Company.

7. The acrylic emulsion for heat sealing paper according to claim 1, characterized in that: The crosslinking monomer is selected from at least one of vinyl trimethoxysilane, glycidyl methacrylate, isobornyl methacrylate, and trimethylolpropane trimethacrylate.

8. The acrylic emulsion for heat sealing paper according to claim 1, characterized in that: The carboxyl functional monomer is selected from one or more combinations of acrylic acid, itaconic acid, maleic acid, and maleic anhydride.

9. The acrylic emulsion for heat-sealing paper according to claim 1, characterized in that: The hydroxyl functional monomer is selected from one or more combinations of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate.

10. A method for preparing an acrylic emulsion for heat-sealing paper, characterized in that: For preparing the emulsion according to any one of claims 1 to 9, the method comprises the steps of: a. Preparation of the bottom liquid A: 60 to 68 parts of deionized water and 0.7 to 2.2 parts of an emulsifier were added to a polymerization reactor, and the temperature was raised to 80 to 90 ° C in the reactor to obtain a bottom liquid A; b. Preparation of pre-emulsion B: Add 22-28 parts of butyl acrylate, 3-6 parts of isooctyl acrylate, 37-45 parts of styrene, 2-4 parts of carboxyl functional monomer, 1-2 parts of hydroxyl functional monomer, 0.5-1 part of cross-linking monomer, 2-4 parts of wax emulsion, 22-26 parts of deionized water, and 0.3-0.8 parts of emulsifier into a pre-emulsification tank, stir and mix to form a uniform pre-emulsion to obtain pre-emulsion B; c. Preparation of initiator solution C: Add 1 to 2 parts of initiator and 13 to 16 parts of deionized water to the initiator tank and mix well to obtain initiator solution C; d. Add 3% to 6% of pre-emulsion B and 10% to 20% of initiator solution C to the polymerization reactor, stir at 80 to 90 ° C for 10 to 30 minutes, and then add the remaining pre-emulsion B and initiator solution C dropwise at a constant flow, and the addition time is controlled at 180 to 220 minutes; e. When the amount of pre-emulsion B remains at 30% to 40%, stop adding pre-emulsion B and initiator solution C, add 3 to 5 parts of acrylic acid monomer long-chain ester to the remaining pre-emulsion B, mix well, and resume adding the remaining pre-emulsion B and initiator solution C; f. After the addition is complete, keep warm at 80-90°C for 1-2 hours; g. Cool down to 40-50°C, add defoamer and bactericide to the reaction kettle, stir for 0.5-1h, filter the material to obtain acrylic emulsion for heat sealing paper.

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