Vinyl acetate copolymer as well as preparation method and application thereof

Abstract

The invention provides a vinyl acetate copolymer as well as a preparation method and application thereof, and belongs to the technical field of high polymer material preparation. According to the invention, active groups such as hydroxyl, epoxy group or amido are introduced to a polymerization molecular chain of polyvinyl acetate in a copolymerization manner, and the vinyl acetate copolymer is prepared by regulating and controlling the feeding ratio, the feeding manner, the reaction temperature and time, the heating rate and the like. When the vinyl acetate copolymer is used as an adhesive, active groups such as hydroxyl, epoxy group, amino and the like on a polymeric molecular chain of the vinyl acetate copolymer can directly react with various curing agents, so that the performance of the vinyl acetate adhesive is improved, and the vinyl acetate copolymer particularly has outstanding heat resistance, bonding strength and environmental protection property; meanwhile, active groups are introduced into a polymeric molecular chain, and other materials containing hydroxyl can be reduced, so that the vinyl acetate copolymer adhesive disclosed by the invention has better material compatibility, and the application space of the adhesive is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material preparation, and particularly relates to a vinyl acetate copolymer, a preparation method thereof, and an application thereof. Background Art

[0002] Polyvinyl acetate used as an adhesive is generally an emulsion type product, such as white emulsion glue, which is a non-toxic, odorless, non-flammable and non-explosive environmental protection adhesive type that does not pollute the environment during use. As a water-based adhesive, polyvinyl acetate emulsion has disadvantages such as slow curing speed and poor water resistance, which greatly limit its application.

[0003] There are the following two ways for the curing mechanism of polyvinyl acetate emulsion adhesives: One is that the polyvinyl acetate in emulsion form forms a film and cures as the water evaporates after sizing. The curing agents such as boric acid added are actually auxiliaries to promote the flocculation of polyvinyl acetate particles in the emulsion to form a film, rather than a cross-linking mechanism of a chemical reaction type; The other is to add a curing agent such as isocyanate for curing. The curing mechanism of isocyanate itself is to react and cross-link with hydroxyl or amino groups for curing. However, there are no groups in the polymer molecular chain of polyvinyl acetate emulsion that can react with isocyanate. In fact, the curing agents such as isocyanate react with the water in polyvinyl acetate emulsion or the hydroxyl groups in the dispersant to achieve curing.

[0004] In order to realize the reaction between polyvinyl acetate emulsion and the curing agent to form cross-linking, the method of copolymerization is often used to make the polymer molecular chain in polyvinyl acetate emulsion contain groups that can react with the curing agent. For example, a polyvinyl acetate graft copolymer and its free radical / cation conversion polymerization method disclosed in Patent CN101067013A is to directly modify partially hydrolyzed polyvinyl acetate to obtain its active hydroxyl groups to facilitate graft copolymerization reaction. The partially hydrolyzed polyvinyl acetate used in this method is prepared by acid hydrolysis. Compared with alkaline hydrolysis, the acid hydrolysis process is relatively slow, and the hydrolysis process has complex technology and great difficulty in process control. A polyvinyl acetate copolymer emulsion disclosed in Patent CN101121768A is copolymerization modified for vinyl acetate during emulsion polymerization by adding a water-resistant monomer, vinyl versatate. This method can improve water resistance to a certain extent, but since the glass transition temperature of vinyl versatate is < -10 °C, the copolymerized vinyl acetate film is relatively soft, which will significantly reduce the rigidity of the board when applied to the field of wood-based panels. A preparation method of a formaldehyde-free and highly water-resistant polyvinyl acetate wood adhesive disclosed in Patent CN111876099A uses acrylate monomers for copolymerization reaction, and polyvinyl alcohol is used as a dispersant. A relatively toxic aziridine is used as a cross-linking agent at 1% to prepare woodworking glue, realizing the formaldehyde-free of the finger-jointed wood adhesive, but the performance has not been significantly improved.

[0005] In summary, at present, when polyvinyl acetate is used as an adhesive, it either relies on film formation, or the curing agent reacts with the hydroxyl groups in the dispersant / solvent water, or monomers such as acrylate monomers that require special curing agents to initiate cross-linking are introduced for copolymerization. None of the above methods have achieved cross-linking with the polyvinyl acetate polymer body and the effect of environmental protection in operation. SUMMARY OF THE INVENTION

[0006] In view of the above deficiencies of the prior art, the present invention provides a vinyl acetate copolymer, a preparation method thereof and an application thereof. By copolymerization, active groups such as hydroxyl groups, epoxy groups or amino groups are introduced into the polymer molecular chain of polyvinyl acetate, so that a curing agent can directly react with the polyvinyl acetate polymer body to produce chain extension or cross-linking, improve the curing speed, enhance the water resistance of polyvinyl acetate, and expand the scope of application of polyvinyl acetate adhesives.

[0007] To achieve the above object, the specific technical solutions of the present invention are as follows:

[0008] The present invention provides a method for preparing a vinyl acetate copolymer, comprising the following steps:

[0009] (1) Mix uniformly the raw materials including 100% of the feeding amount of the solvent, 5%-50% of the feeding amount of vinyl acetate, 0-100% of the feeding amount of the comonomer, 5%-50% of the feeding amount of the initiator, and 0-100% of the feeding amount of the chain regulator; wherein, the comonomer is an alkenyl monomer containing at least one functional group of hydroxyl group, epoxy group or amino group;

[0010] (2) Raise the temperature of the material to temperature I, start timing after the temperature reaches temperature I, react the raw materials for 15-120 min, and at the same time control the temperature of the material to be temperature II at the 15-120th min; the temperature II is: raised by 5-45 °C on the basis of temperature I;

[0011] (3) Drop the remaining vinyl acetate, comonomer, initiator and chain regulator into the reaction system, and control the temperature of the material to rise to temperature III while dropping; the temperature III is: raised by 0-60 °C on the basis of temperature II;

[0012] (4) After the dropping is completed, continue to react at temperature III for a period of time and gradually reduce the rotation speed;

[0013] (5) After the reaction is completed, cool down, discharge the material, and obtain the vinyl acetate copolymer.

[0014] The present invention prepares a vinyl acetate copolymer by copolymerizing to introduce active groups such as hydroxyl groups, epoxy groups or amino groups onto the polymer molecular chain of polyvinyl acetate. When the vinyl acetate copolymer is used as an adhesive, the active groups such as hydroxyl groups, epoxy groups and amino groups on its polymer molecular chain can directly react with various curing agents, improving the performance of vinyl acetate adhesives, especially being outstanding in heat resistance, bonding strength and environmental friendliness. At the same time, by introducing active groups into the polymer molecular chain, the present invention can also reduce the additional addition of other materials containing hydroxyl groups, making the vinyl acetate copolymer adhesives of the present invention have better material compatibility. However, when introducing active groups such as hydroxyl groups, epoxy groups or amino groups into the polymer molecular chain, there are often differences in the physical properties of the polymerization monomers and multiple-step reactions, resulting in relatively difficult process control. Therefore, during the preparation process, the present invention controls the rate of the polymerization reaction by adjusting the feeding ratio, feeding method, reaction temperature and time, and heating rate, and prepares vinyl acetate copolymers with different viscosity numbers and good comprehensive performance, realizing the wide application of vinyl acetate copolymer resins in the field of adhesives. In addition, by regulating the amount of the comonomer, vinyl acetate copolymers with different functionality can be prepared, further expanding the application space of such adhesives.

[0015] Preferably, the weight ratio of the solvent, vinyl acetate, comonomer, initiator and chain regulator is (5 - 200) : 100 : (2.5 - 50) : (0.05 - 0.5) : (0 - 5).

[0016] Preferably, in step (2), the temperature I is 30 - 120 °C.

[0017] Preferably, in step (3), the dropping time is 1 - 12 h.

[0018] Preferably, in step (4), after the dropping is completed, continue to react at temperature III for 1 - 6 h.

[0019] Preferably, in step (5), cool down to 40 - 60 °C for discharging.

[0020] Preferably, in step (5), after discharging, remove the solvent from the obtained mixture at 40 - 90 °C and a vacuum degree of 0.025 - 0.1 MPa, and obtain the finished product of the vinyl acetate copolymer through crushing or pelletizing.

[0021] Preferably, the comonomer includes but is not limited to at least one of 2-hydroxyethyl acrylate (2-HEA), 4-hydroxybutyl acrylate (4-HBA), hydroxypropyl acrylate (HPA), amyl hydroxyacrylate, isoamyl hydroxyacrylate, 2-hydroxyethyl methacrylate (HEMA), 2-hydroxybutyl methacrylate (2-HPBA), hydroxypropyl methacrylate (HPMA), amyl hydroxy methacrylate, phenyl hydroxyacrylate, phenyl hydroxy methacrylate, tert-butyl hydroxy methacrylate, trimethylolpropane monoacrylate, hydroxyethyl methacrylate phosphate, hydroxyethyl caprolactone acrylate, 4-hydroxycyclohexyl methacrylate, N-hydroxymethylacrylamide (NMA), acrylamide, N-butoxymethyl(meth)acrylamide, ethyl 3-aminocrotonate, 3-aminoacrylate, epoxy acrylate, epoxy methacrylate, bisphenol A epoxy acrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl acrylate.

[0022] Preferably, the solvent includes but is not limited to at least one of isopropanol, methanol, ethanol, n-butanol, acetone, ethyl acetate, methyl acetate, butyl acetate, benzene, toluene, chloroform, carbon tetrachloride.

[0023] Preferably, the initiator includes but is not limited to at least one of azobisisobutyronitrile (AIBN), azobisisoheptonitrile (ABVN), benzoyl peroxide (BPO), bis(3,5,6-trimethylhexanoyl) peroxide, tert-butyl peroxyneopentanoate, cumyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate, dimethyl 2,2'-azobis(2-methylpropionate), azoisobutyronitrile carboxamide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, di-tert-butyl peroxide.

[0024] Preferably, the chain regulator includes but is not limited to a chain transfer agent and / or a chain extender; wherein, the chain transfer agent includes but is not limited to at least one of 2-mercaptoethanol, methanethiol, ethanethiol, acetaldehyde, dodecyl mercaptan, carbon tetrachloride, dichloromethane, n-butyl mercaptan, octyl mercaptan; the chain extender includes but is not limited to at least one of ethylenediamine (EDA), N-isopropylethylenediamine (IPEDA), triethylenetetramine (TETA), diethylenetriamine (DETA), diphenylmethane diisocyanate (MDI), dimethylthiotoluenediamine (DMTDA), 1,4-butanediol (BDO), neopentyl glycol (NPG), sorbitol, diethylene glycol (DEG), triethylene glycol, trimethylolpropane (TMP), diethylaminoethanol (DEAE), N,N-dihydroxy(diisopropyl)aniline (HPA).

[0025] The present invention also provides a vinyl acetate copolymer prepared by the method.

[0026] The present invention also provides the application of the vinyl acetate copolymer in the field of adhesives.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] In the present invention, through copolymerization, vinyl monomers with active groups such as hydroxyl groups, epoxy groups, and amino groups are copolymerized with vinyl acetate. The molecular chains of the obtained vinyl acetate copolymer in bulk polymerization have more active functional groups, which are more likely to directly react with various curing agents, improving the comprehensive performance of vinyl acetate adhesives and realizing the wide application of vinyl acetate copolymer resins in the field of adhesives. In addition, by adjusting the amount of copolymer monomers, vinyl acetate copolymers with different functionality can be prepared, further expanding the application fields of such adhesives. Specifically, the application of the vinyl acetate copolymer of the present invention in PUR (moisture-curing reaction-type polyurethane hot melt adhesive) adhesives has the following advantages:

[0029] (1) Enhancing compatibility and chemical crosslinking with PUR

[0030] The active groups such as hydroxyl groups, epoxy groups, and amino groups introduced by the vinyl acetate copolymer of the present invention can react chemically with the isocyanate groups (-NCO) in PUR to form stable urethane bonds. This chemical crosslinking effect significantly improves the compatibility between the vinyl acetate copolymer and PUR, enhances the interfacial bonding force between the two, and thus improves the bonding strength and durability of the overall adhesive. For example, in composite materials, the vinyl acetate copolymer of the present invention as an intermediate layer can effectively bridge PUR and the substrate, reducing interfacial defects.

[0031] (2) Improving thermal stability and hydrolysis resistance

[0032] The vinyl acetate copolymer of the present invention can optimize the thermal properties of vinyl acetate copolymer adhesives. Specifically, the glass transition temperature (Tg) of the vinyl acetate copolymer emulsion adhesive decreases, while the thermal stability improves. This is due to the three-dimensional network structure formed after the crosslinking of the active groups such as hydroxyl groups, epoxy groups, and amino groups with PUR, reducing creep and degradation at high temperatures. In addition, the crosslinked structure formed by the reaction of the active groups such as hydroxyl groups, epoxy groups, and amino groups with PUR can also enhance the hydrolysis resistance, reducing the influence of environmental moisture on the adhesive layer, and is suitable for applications in humid or high-temperature environments.

[0033] (3) Optimizing mechanical properties

[0034] The vinyl acetate copolymer of the present invention can improve the flexibility and impact resistance of adhesives by adjusting the ratio of soft and hard segments. For example, when the vinyl acetate copolymer grafts a polyurethane derivative macromonomer, the increase in comonomers reduces the rigidity of the system, enabling the adhesive layer to have better ductility while maintaining high peel strength. This property is particularly suitable for scenarios requiring resistance to repeated stress, such as automotive interiors or electronic component encapsulation.

[0035] (4)Reduce the system viscosity and improve the processing performance

[0036] The vinyl acetate copolymer of the present invention has good hydrophilicity and dispersibility, can reduce the viscosity of PUR adhesives in the high-temperature molten state, and improve the uniformity of coating and spraying processes. This property is particularly important in automated production lines, which can improve production efficiency and reduce energy consumption.

[0037] (5)Environmental protection and versatility

[0038] As a component of water-based adhesives, the vinyl acetate copolymer of the present invention can reduce the VOC emissions of traditional solvent-based adhesives, meeting the environmental protection trend. At the same time, its composite system with PUR can balance high bonding strength and low curing temperature, and is suitable for fields with strict requirements for environmental protection and process conditions, such as furniture manufacturing and electronic encapsulation. Specific embodiments

[0039] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0040] The present invention provides a preparation method of a vinyl acetate copolymer, comprising the following steps:

[0041] (1)Mix evenly the raw materials including 100% of the feeding amount of solvent, 5%-50% of the feeding amount of vinyl acetate, 0-100% of the feeding amount of comonomer, 5%-50% of the feeding amount of initiator, and 0-100% of the feeding amount of chain regulator; wherein, the comonomer is an alkenyl monomer containing at least one functional group of hydroxyl, epoxy group, or amino group;

[0042] (2)Raise the material temperature to temperature I, start timing after the temperature reaches temperature I, react the raw materials for 15-120 min, and at the same time control the material temperature to be temperature II at the 15-120th min; the temperature II is: increased by 5-45°C based on temperature I;

[0043] (3) Add the remaining vinyl acetate, comonomer, initiator, and chain regulator to the reaction system, and while adding, control the temperature of the material to rise to Temperature III; Temperature III is: increased by 0 - 60 °C based on Temperature II;

[0044] (4) After the addition is completed, continue to react at Temperature III for a period of time, and gradually reduce the rotation speed;

[0045] (5) After the reaction is completed, cool down, discharge the material, and obtain the vinyl acetate copolymer.

[0046] In some examples, the weight ratio of the solvent, vinyl acetate, comonomer, initiator, and chain regulator is (5 - 200) : 100 : (2.5 - 50) : (0.05 - 0.5) : (0 - 5).

[0047] In some examples, in step (2), Temperature I is 30 - 120 °C.

[0048] In some examples, in step (3), the addition time is 1 - 12 h.

[0049] In some examples, in step (4), after the addition is completed, continue to react at Temperature III for 1 - 6 h.

[0050] In some examples, in step (5), cool down to 40 - 60 °C and then discharge the material.

[0051] In some examples, in step (5), after discharging the material, remove the solvent from the obtained mixture at 40 - 90 °C and a vacuum degree of 0.025 - 0.1 MPa, and obtain the finished vinyl acetate copolymer through crushing or pelletizing.

[0052] In some examples, the comonomer includes but is not limited to at least one of 2 - hydroxyethyl acrylate (2 - HEA), 4 - hydroxybutyl acrylate (4 - HBA), hydroxypropyl acrylate (HPA), pentyl hydroxyacrylate, isopentyl hydroxyacrylate, 2 - hydroxyethyl methacrylate (HEMA), 2 - hydroxypropyl methacrylate (2 - HPBA), hydroxypropyl methacrylate (HPMA), pentyl hydroxymethacrylate, phenyl hydroxyacrylate, phenyl hydroxymethacrylate, tert - butyl hydroxymethacrylate, trimethylolpropane monoacrylate, hydroxyethyl methacrylate phosphate, hydroxyethyl caprolactone acrylate, 4 - hydroxycyclohexyl methacrylate, N - hydroxymethyl acrylamide (NMA), acrylamide, N - butoxymethyl(meth)acrylamide, ethyl 3 - aminobutyrate, 3 - aminoacrylate, epoxy acrylate, epoxy methacrylate, bisphenol A epoxy acrylate, 3,4 - epoxycyclohexylmethyl methacrylate, glycidyl acrylate.

[0053] In some examples, the solvent includes, but is not limited to, at least one of isopropyl alcohol, methanol, ethanol, n-butanol, acetone, ethyl acetate, methyl acetate, butyl acetate, benzene, toluene, chloroform, and carbon tetrachloride.

[0054] In some examples, the initiator includes, but is not limited to, at least one of azobisisobutyronitrile (AIBN), azobisisoheptonitrile (ABVN), benzoyl peroxide (BPO), bis(3,5,6-trimethylhexanoyl) peroxide, tert-butyl peroxyneodecanoate, cumyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate, dimethyl 2,2'-azobis(2-methylpropionate), azoisobutyronitrile carboxamide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, and di-tert-butyl peroxide.

[0055] In some examples, the chain regulator includes, but is not limited to, a chain transfer agent and / or a chain extender; wherein, the chain transfer agent includes, but is not limited to, at least one of 2-mercaptoethanol, methanethiol, ethanethiol, acetaldehyde, dodecyl mercaptan, carbon tetrachloride, dichloromethane, n-butyl mercaptan, and octyl mercaptan; the chain extender includes, but is not limited to, at least one of ethylenediamine (EDA), N-isopropylethylenediamine (IPEDA), triethylenetetramine (TETA), diethylenetriamine (DETA), diphenylmethane diisocyanate (MDI), dimethylthiotoluenediamine (DMTDA), 1,4-butanediol (BDO), neopentyl glycol (NPG), sorbitol, diethylene glycol (DEG), triethylene glycol, trimethylolpropane (TMP), diethylaminoethanol (DEAE), and N,N-dihydroxy(diisopropyl)aniline (HPA).

[0056] In the following specific examples, unless otherwise specified, the raw materials or reagents used are obtained by conventional purchase.

[0057] Example 1

[0058] A vinyl acetate copolymer, wherein the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0059] Its preparation method includes the following steps:

[0060] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropyl alcohol, 15% of the feeding amount of vinyl acetate, 0% of the feeding amount of butyl hydroxyacrylate, 15% of the feeding amount of azobisisobutyronitrile, and 15% of the feeding amount of mercaptoethanol to the closed polymerization reaction kettle;

[0061] (b)Under stirring, raise the temperature of the material to 63 °C. After the temperature reaches 63 °C, start timing and react the raw materials for 30 min. At the same time, control the temperature of the material to be 75 °C at the 17th minute (for the remaining 13 min, maintain the temperature of the material at 75 °C for the reaction);

[0062] (c)Uniformly add the remaining vinyl acetate, butyl acrylate, azobisisobutyronitrile, and mercaptoethanol to the reaction system while controlling the temperature of the material to rise to 84 °C at the same time. The dropping time is controlled within 4 h. After the temperature of the material reaches 84 °C, stabilize the temperature of the material during the dropping process at 84 °C;

[0063] (d)After the dropping is completed, continue to react at 84 °C for 4 h and gradually reduce the rotation speed to 150 rpm;

[0064] (e)After the reaction is completed, cool down to 50 °C and discharge the material;

[0065] (f)Remove the solvent at 85 °C and 0.1 MPa vacuum and then crush to obtain the finished product of vinyl acetate copolymer.

[0066] Carry out tests on the conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality of the obtained finished product of vinyl acetate copolymer, and the test results are shown in Table 1.

[0067] Example 2

[0068] A vinyl acetate copolymer, in which the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:6.25:0.2:2.5.

[0069] Its preparation method includes the following steps:

[0070] (a)Start the stirring of the deoxygenated reaction kettle, and add 100% feed amount of isopropanol, 15% feed amount of vinyl acetate, 0% feed amount of butyl acrylate, 15% feed amount of azobisisobutyronitrile, and 15% feed amount of mercaptoethanol into the closed polymerization reaction kettle;

[0071] (b)Under stirring, raise the temperature of the material to 62.4 °C. After the temperature reaches 62.4 °C, start timing and react the raw materials for 30 min. At the same time, control the temperature of the material to be 75 °C at the 17th minute (for the remaining 13 min, maintain the temperature of the material at 75 °C for the reaction);

[0072] (c)Uniformly add the remaining vinyl acetate, butyl acrylate, azobisisobutyronitrile, and mercaptoethanol to the reaction system while controlling the temperature of the material to rise to 84 °C at the same time. The dropping time is controlled within 4 h. After the temperature of the material reaches 84 °C, stabilize the temperature of the material during the dropping process at 84 °C;

[0073] (d) After the dropping is completed, continue the reaction at 84 °C for 4 h and gradually reduce the rotation speed to 150 rpm;

[0074] (e) After the reaction is completed, cool down to 50 °C and discharge the material;

[0075] (f) Remove the solvent at 85 °C and 0.1 MPa vacuum and then crush to obtain the finished product of vinyl acetate copolymer.

[0076] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0077] Example 3

[0078] A vinyl acetate copolymer, in which the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:15:0.175:1.

[0079] Its preparation method includes the following steps:

[0080] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% feeding amount of isopropanol, 15% feeding amount of vinyl acetate, 0% feeding amount of ethyl hydroxyacrylate, 15% feeding amount of azobisisobutyronitrile, and 15% feeding amount of mercaptoethanol into the closed polymerization reaction kettle;

[0081] (b) Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 30 min, and at the same time control the material temperature to be 75 °C at the 27th minute (for the remaining 3 min, maintain the material temperature at 75 °C for the reaction);

[0082] (c) Drop the remaining vinyl acetate, butyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a constant speed. While dropping, start to control the material temperature to rise to 84 °C, and control the dropping time within 4 h; after the material temperature reaches 84 °C, keep the material temperature during the dropping process stable at 84 °C;

[0083] (d) After the dropping is completed, continue the reaction at 84 °C for 4 h and gradually reduce the rotation speed to 150 rpm;

[0084] (e) After the reaction is completed, cool down to 50 °C and discharge the material;

[0085] (f) Remove the solvent at 88 °C and 0.06 MPa vacuum and then crush to obtain the finished product of vinyl acetate copolymer.

[0086] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0087] Example 4

[0088] A vinyl acetate copolymer, wherein the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:9.25:0.175:1.

[0089] Its preparation method includes the following steps:

[0090] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropanol, 15% of the feeding amount of vinyl acetate, 0% of the feeding amount of ethyl hydroxyacrylate, 15% of the feeding amount of azobisisobutyronitrile, and 15% of the feeding amount of mercaptoethanol into the closed polymerization reaction kettle;

[0091] (b) Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 30 min, and at the same time control the material temperature to be 73 °C at the 27th minute (for the remaining 3 min, maintain the material temperature at 73 °C for reaction);

[0092] (c) Drop the remaining vinyl acetate, butyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a uniform speed. While dropping, start to control the material temperature to rise to 84 °C, and the dropping time is controlled within 4 h; after the material temperature reaches 84 °C, stabilize the material temperature during the dropping process at 84 °C;

[0093] (d) After the dropping is completed, continue to react at 84 °C for 4 h, and gradually reduce the rotation speed to 150 rpm;

[0094] (e) After the reaction ends, cool down to 50 °C and discharge the material;

[0095] (f) Remove the solvent at 85 °C and 0.1 MPa vacuum degree, and then crush to obtain the finished product of vinyl acetate copolymer.

[0096] Perform conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality tests on the obtained finished product of vinyl acetate copolymer, and the test results are shown in Table 1.

[0097] Example 5

[0098] A vinyl acetate copolymer, wherein the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0099] Its preparation method includes the following steps:

[0100] (a) Start the stirring of the deoxygenated reaction kettle, and add isopropanol with 100% of the feeding amount, vinyl acetate with 14% of the feeding amount, butyl hydroxyacrylate with 0% of the feeding amount, azobisisobutyronitrile with 14% of the feeding amount, and mercaptoethanol with 14% of the feeding amount into the closed polymerization reaction kettle;

[0101] (b) While stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 60 min, and at the same time control the material temperature to be 75 °C at the 60th min (when the material temperature reaches 75 °C, proceed to the next step);

[0102] (c) Drop the remaining vinyl acetate, butyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a uniform speed. While dropping, start to control the material temperature to rise to 84 °C, and the dropping time is controlled within 4 h; after the material temperature reaches 84 °C, keep the material temperature during the dropping process at 84 °C;

[0103] (d) After the dropping is completed, continue to react at 84 °C for 4 h, and gradually reduce the rotation speed to 150 rpm;

[0104] (e) After the reaction is completed, cool down to 50 °C and discharge the material;

[0105] (f) Remove the solvent at 85 °C and 0.1 MPa vacuum degree, and then crush to obtain the finished product of vinyl acetate copolymer.

[0106] Test the obtained finished product of vinyl acetate copolymer for conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality. The test results are shown in Table 1.

[0107] Example 6

[0108] A vinyl acetate copolymer, and the weight ratio of its raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:18:0.175:1.

[0109] Its preparation method includes the following steps:

[0110] (a) Start the stirring of the deoxygenated reaction kettle, and add isopropanol with 100% of the feeding amount, vinyl acetate with 14% of the feeding amount, butyl hydroxyacrylate with 0% of the feeding amount, azobisisobutyronitrile with 14% of the feeding amount, and mercaptoethanol with 14% of the feeding amount into the closed polymerization reaction kettle;

[0111] (b) While stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 45 min, and at the same time control the material temperature to be 73 °C at the 30th min (for the remaining 15 min, maintain the material temperature at 73 °C for the reaction);

[0112] (c) The remaining vinyl acetate, butyl acrylate hydroxy, azodiisobutyronitrile, and mercaptoethanol were uniformly added dropwise to the reaction system. While adding the drops, the temperature of the material was started to be increased to 84 °C, and the dropping time was controlled within 4 h. After the material temperature reached 84 °C, the material temperature during the dropping process was stabilized at 84 °C;

[0113] (d) After the dropping was completed, the reaction was continued at 84 °C for 4 h, and the rotation speed was gradually reduced to 150 rpm;

[0114] (e) After the reaction ended, the temperature was decreased to 50 °C for discharging;

[0115] (f) After removing the solvent at 85 °C and 0.1 MPa vacuum, it was crushed to obtain the finished product of vinyl acetate copolymer.

[0116] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0117] Example 7

[0118] A vinyl acetate copolymer, in which the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:2.

[0119] Its preparation method includes the following steps:

[0120] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropanol, 12% of the feeding amount of vinyl acetate, 0% of the feeding amount of butyl acrylate hydroxy, 12% of the feeding amount of azodiisobutyronitrile, and 24% of the feeding amount of mercaptoethanol into the closed polymerization reaction kettle;

[0121] (b) While stirring, increase the temperature of the material to 62 °C. After the temperature reaches 62 °C, start timing, and react the raw materials for 30 min. At the same time, control the material temperature to be 73 °C at the 17th minute (for the remaining 13 minutes, maintain the material temperature at 73 °C for the reaction);

[0122] (c) The remaining vinyl acetate, butyl acrylate hydroxy, benzoyl peroxide, and mercaptoethanol were uniformly added dropwise to the reaction system. While adding the drops, the temperature of the material was started to be increased to 86 °C, and the dropping time was controlled within 4 h. After the material temperature reached 86 °C, the material temperature during the dropping process was stabilized at 86 °C;

[0123] (d) After the dropping was completed, the reaction was continued at 86 °C for 4 h, and the rotation speed was gradually reduced to 150 rpm;

[0124] (e) After the reaction ended, the temperature was decreased to 50 °C for discharging;

[0125] (f)The vinyl acetate copolymer product is obtained by removing the solvent at 70 °C and a vacuum of 0.05 MPa and then crushing.

[0126] The obtained vinyl acetate copolymer product is subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0127] Example 8

[0128] A vinyl acetate copolymer, in which the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:10:0.125:0.

[0129] Its preparation method includes the following steps:

[0130] (a)Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropanol, 12% of the feeding amount of vinyl acetate, 5% of the feeding amount of butyl hydroxyacrylate, and 12% of the feeding amount of azobisisobutyronitrile into the closed polymerization reaction kettle;

[0131] (b)Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 45 min, and at the same time control the material temperature to be 75 °C at the 25th min (for the remaining 20 min, maintain the material temperature at 75 °C for reaction);

[0132] (c)Drop the remaining vinyl acetate, butyl hydroxyacrylate, and azobisisobutyronitrile into the reaction system at a uniform speed. While dropping, start to control the material temperature to rise to 84 °C, and the dropping time is controlled within 4 h; after the material temperature reaches 84 °C, stabilize the material temperature during the dropping process at 84 °C;

[0133] (d)After the dropping is completed, continue to react at 84 °C for 3 h, and gradually reduce the rotation speed to 50 rpm;

[0134] (e)After the reaction ends, cool down to 50 °C and discharge the material;

[0135] (f)The vinyl acetate copolymer product is obtained by removing the solvent at 85 °C and a vacuum of 0.1 MPa and then crushing.

[0136] The obtained vinyl acetate copolymer product is subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0137] Example 9

[0138] A vinyl acetate copolymer, in which the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0139] The preparation method comprises the following steps:

[0140] (a) Start the stirring of the deoxygenated reaction kettle, and add methanol with a feeding amount of 100%, vinyl acetate with a feeding amount of 15%, butyl hydroxyacrylate with a feeding amount of 0%, azobisisobutyronitrile with a feeding amount of 15%, and mercaptoethanol with a feeding amount of 15% into the closed polymerization reaction kettle;

[0141] (b) Under stirring, raise the temperature of the materials to 63 °C. After the temperature reaches 63 °C, start timing, and react the raw materials for 45 min. At the same time, control the temperature of the materials to be 75 °C at the 30th min (for the remaining 15 min, maintain the temperature of the materials at 75 °C for reaction);

[0142] (c) Drop the remaining vinyl acetate, butyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a uniform speed. While dropping, start to control the temperature of the materials to rise to 80 °C, and control the dropping time to be 6 h. After the temperature of the materials reaches 80 °C, stabilize the temperature of the materials during the dropping process at 80 °C;

[0143] (d) After the dropping is completed, continue to react at 80 °C for 4 h, and gradually reduce the rotation speed to 50 rpm;

[0144] (e) After the reaction is completed, cool down to 50 °C and discharge the materials;

[0145] (f) Remove the solvent at 68 °C and a vacuum degree of 0.06 MPa, and then crush to obtain the finished product of vinyl acetate copolymer.

[0146] Test the obtained finished product of vinyl acetate copolymer for conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0147] Example 10

[0148] A vinyl acetate copolymer, wherein the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0149] The preparation method comprises the following steps:

[0150] (a) Start the stirring of the deoxygenated reaction kettle, and add isopropanol with a feeding amount of 100%, vinyl acetate with a feeding amount of 25%, butyl hydroxyacrylate with a feeding amount of 25%, azobisisobutyronitrile with a feeding amount of 25%, and dodecyl mercaptan with a feeding amount of 100% into the closed polymerization reaction kettle;

[0151] (b) Raise the temperature of the material to 62 °C with stirring. After the temperature reaches 62 °C, start timing and react the raw materials for 30 min. At the same time, control the temperature of the material to be 73 °C at the 22nd min (for the remaining 8 min, maintain the temperature of the material at 73 °C for the reaction);

[0152] (c) Slowly add the remaining vinyl acetate, butyl acrylate, and azobisisobutyronitrile to the reaction system while controlling the temperature of the material to rise to 84 °C. The dropping time is controlled within 4 h. After the temperature of the material reaches 84 °C, stabilize the temperature of the material during the dropping process at 84 °C;

[0153] (d) After the dropping is completed, continue to react at 84 °C for 4 h and gradually reduce the rotation speed to 50 rpm;

[0154] (e) After the reaction is completed, cool down to 50 °C and discharge the material;

[0155] (f) Remove the solvent at 85 °C and a vacuum degree of 0.06 MPa, and then crush to obtain the finished product of vinyl acetate copolymer.

[0156] Test the obtained finished product of vinyl acetate copolymer for conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality. The test results are shown in Table 1.

[0157] Example 11

[0158] A vinyl acetate copolymer, wherein the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 25:100:8.175:0.15:1.8.

[0159] Its preparation method includes the following steps:

[0160] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropyl alcohol, 15% of the feeding amount of vinyl acetate, 0% of the feeding amount of butyl acrylate, 15% of the feeding amount of azobisisobutyronitrile, and 25% of the feeding amount of dodecyl mercaptan to the closed polymerization reaction kettle;

[0161] (b) Raise the temperature of the material to 62 °C with stirring. After the temperature reaches 62 °C, start timing and react the raw materials for 30 min. At the same time, control the temperature of the material to be 73 °C at the 30th min (when the temperature of the material reaches 73 °C, proceed to the next step);

[0162] (c) Slowly add the remaining vinyl acetate, ethyl acrylate, azobisisobutyronitrile, and dodecyl mercaptan to the reaction system while controlling the temperature of the material to rise to 84 °C. The dropping time is controlled within 8 h. After the temperature of the material reaches 84 °C, stabilize the temperature of the material during the dropping process at 84 °C;

[0163] (d)After the dropping is completed, continue the reaction at 84 °C for 4 h and gradually reduce the rotation speed to 50 rpm;

[0164] (e)After the reaction is completed, cool down to 50 °C and discharge the material;

[0165] (f)Remove the solvent at 85 °C and 0.08 MPa vacuum and then crush to obtain the finished product of vinyl acetate copolymer.

[0166] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0167] Example 12

[0168] A vinyl acetate copolymer, wherein the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.175:0.175:1.

[0169] Its preparation method includes the following steps:

[0170] (a)Start the stirring of the deoxygenated reaction kettle, and add isopropyl alcohol with 100% feeding amount, vinyl acetate with 14% feeding amount, 3 - aminoacrylate with 0% feeding amount, azobisisobutyronitrile with 14% feeding amount, and mercaptoethanol with 14% feeding amount into the closed polymerization reaction kettle;

[0171] (b)Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 30 min, and at the same time control the material temperature to be 73 °C at the 30th min (when the material temperature reaches 73 °C, proceed to the next step);

[0172] (c)Drop the remaining vinyl acetate, 3 - aminoacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a constant speed. While dropping, start to control the material temperature to rise to 84 °C, and control the dropping time within 4 h; after the material temperature reaches 84 °C, keep the material temperature during the dropping process stable at 84 °C;

[0173] (d)After the dropping is completed, continue the reaction at 84 °C for 4 h and gradually reduce the rotation speed to 150 rpm;

[0174] (e)After the reaction is completed, cool down to 50 °C and discharge the material;

[0175] (f)Remove the solvent at 85 °C and 0.1 MPa vacuum and then crush to obtain the finished product of vinyl acetate copolymer.

[0176] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0177] Example 13

[0178] A vinyl acetate copolymer, the weight ratio of its raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.2:1.

[0179] Its preparation method includes the following steps:

[0180] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropanol, 14% of the feeding amount of vinyl acetate, 0% of the feeding amount of epoxy acrylate, 14% of the feeding amount of azobisisobutyronitrile, and 14% of the feeding amount of mercaptoethanol into the closed polymerization reaction kettle;

[0181] (b) Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 30 min, and at the same time control the material temperature to be 75 °C at the 25th min (for the remaining 5 min, maintain the material temperature at 75 °C for reaction);

[0182] (c) Drop the remaining vinyl acetate, epoxy acrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a constant speed. While dropping, start to control the material temperature to rise to 84 °C, and the dropping time is controlled within 4 h; after the material temperature reaches 84 °C, stabilize the material temperature during the dropping process at 84 °C;

[0183] (d) After the dropping is completed, continue to react at 84 °C for 4 h, and gradually reduce the rotation speed to 150 rpm;

[0184] (e) When the reaction ends, cool down to 50 °C and discharge the material;

[0185] (f) Remove the solvent at 85 °C and 0.1 MPa vacuum degree, and then crush to obtain the finished product of vinyl acetate copolymer.

[0186] The obtained finished product of vinyl acetate copolymer is subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0187] Example 14

[0188] A vinyl acetate copolymer, the weight ratio of its raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.2:1.

[0189] Its preparation method includes the following steps:

[0190] (a) Start the stirring of the deoxygenated reaction kettle, and add isopropyl alcohol at 100% feed rate, vinyl acetate at 14% feed rate, butyl hydroxyacrylate at 0% feed rate, azobisisobutyronitrile at 14% feed rate, and mercaptoethanol at 14% feed rate into the closed polymerization reaction kettle;

[0191] (b) While stirring, raise the temperature of the materials to 63 °C. After the temperature reaches 63 °C, start timing, and react the raw materials for 30 min. At the same time, control the temperature of the materials to be 75 °C at the 30th minute (when the temperature of the materials reaches 75 °C, proceed to the next step);

[0192] (c) Uniformly add the remaining vinyl acetate, ethyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol to the reaction system. While adding, start to control the temperature of the materials to rise to 84 °C, and the dropping time is controlled within 4 h; after the temperature of the materials reaches 84 °C, keep the temperature of the materials during the dropping process at 84 °C;

[0193] (d) After the dropping is completed, continue to react at 84 °C for 4 h, and gradually reduce the rotation speed to 150 rpm;

[0194] (e) After the reaction is completed, cool down to 50 °C and discharge the materials;

[0195] (f) Remove the solvent at 85 °C and 0.1 MPa vacuum degree, and then crush to obtain the finished product of vinyl acetate copolymer.

[0196] Conduct tests on the conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality of the obtained finished product of vinyl acetate copolymer, and the test results are shown in Table 1.

[0197] Example 15

[0198] A vinyl acetate copolymer, and the weight ratio of its raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.15:1.

[0199] Its preparation method includes the following steps:

[0200] (a) Start the stirring of the deoxygenated reaction kettle, and add isopropyl alcohol at 100% feed rate, vinyl acetate at 14% feed rate, ethyl hydroxyacrylate at 0% feed rate, azobisisobutyronitrile at 14% feed rate, and mercaptoethanol at 100% feed rate into the closed polymerization reaction kettle;

[0201] (b) While stirring, raise the temperature of the materials to 63 °C. After the temperature reaches 63 °C, start timing, and react the raw materials for 30 min. At the same time, control the temperature of the materials to be 75 °C at the 30th minute (when the temperature of the materials reaches 75 °C, proceed to the next step);

[0202] (c) The remaining vinyl acetate, ethyl hydroxyacrylate, and azobisisobutyronitrile were added dropwise to the reaction system at a uniform rate. While adding the drops, the temperature of the material was controlled to rise to 78 °C, and the dropping time was controlled within 6 h. After the material temperature reached 78 °C, the temperature of the material during the dropping process was stabilized at 78 °C;

[0203] (d) After the dropping was completed, the reaction continued at 78 °C for 6 h, and the rotation speed was gradually reduced to 150 rpm;

[0204] (e) After the reaction ended, the temperature was lowered to 50 °C for discharging;

[0205] (f) After removing the solvent at 85 °C and a vacuum degree of 0.1 MPa, it was crushed to obtain the finished product of vinyl acetate copolymer.

[0206] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0207] Example 16

[0208] A vinyl acetate copolymer, in which the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 10:100:8.15:0.175:1.

[0209] Its preparation method includes the following steps:

[0210] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of isopropanol, 14% of the feeding amount of vinyl acetate, 0% of the feeding amount of ethyl hydroxyacrylate, 14% of the feeding amount of azobisisobutyronitrile, and 14% of the feeding amount of mercaptoethanol to the closed polymerization reaction kettle;

[0211] (b) While stirring, raise the temperature of the material to 63 °C. After the temperature reaches 63 °C, start timing, and react the raw materials for 30 min. At the same time, control the temperature of the material to be 75 °C at the 30th min (when the material temperature reaches 75 °C, proceed to the next step);

[0212] (c) The remaining vinyl acetate, ethyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol were added dropwise to the reaction system at a uniform rate. While adding the drops, the temperature of the material was controlled to rise to 78 °C, and the dropping time was controlled within 4 h. After the material temperature reached 78 °C, the temperature of the material during the dropping process was stabilized at 78 °C;

[0213] (d) After the dropping was completed, the reaction continued at 78 °C for 4 h, and the rotation speed was gradually reduced to 150 rpm;

[0214] (e) After the reaction ended, the temperature was lowered to 50 °C for discharging;

[0215] (f)The vinyl acetate copolymer product is obtained by removing the solvent at 85 °C and a vacuum of 0.08 MPa and then crushing.

[0216] The obtained vinyl acetate copolymer product is subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0217] Example 17

[0218] A vinyl acetate copolymer, in which the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0219] Its preparation method includes the following steps:

[0220] (a)Start the stirring of the deoxygenated reaction kettle, and add isopropanol at 100% feeding amount, vinyl acetate at 14% feeding amount, ethyl hydroxyacrylate at 0% feeding amount, azobisisobutyronitrile at 14% feeding amount, and mercaptoethanol at 14% feeding amount into the closed polymerization reaction kettle;

[0221] (b)Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 30 min, and at the same time control the material temperature to be 75 °C at the 30th min (when the material temperature reaches 75 °C, proceed to the next step);

[0222] (c)Drop the remaining vinyl acetate, ethyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a uniform speed. While dropping, start to control the material temperature to rise to 84 °C, and the dropping time is controlled within 4 h; after the material temperature reaches 84 °C, keep the material temperature during the dropping process at 84 °C;

[0223] (d)After the dropping is completed, continue to react at 84 °C for 2 h, and gradually reduce the rotation speed to 150 rpm;

[0224] (e)After the reaction is completed, cool down to 50 °C and discharge the material;

[0225] (f)The vinyl acetate copolymer product is obtained by removing the solvent at 85 °C and a vacuum of 0.1 MPa and then crushing.

[0226] The obtained vinyl acetate copolymer product is subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0227] Example 18

[0228] A vinyl acetate copolymer, in which the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0229] The preparation method comprises the following steps:

[0230] (a)Start the stirring of the deoxygenated reaction kettle, and add isopropanol with a 100% feeding amount, vinyl acetate with a 14% feeding amount, ethyl acrylate hydroxy with a 0% feeding amount, azobisisobutyronitrile with a 14% feeding amount, and mercaptoethanol with a 100% feeding amount into the polymerization reaction kettle;

[0231] (b)Under stirring, raise the temperature of the materials to 63 °C. After the temperature reaches 63 °C, start timing, react the raw materials for 30 minutes, and at the same time control the temperature of the materials to be 75 °C at the 30th minute (when the temperature of the materials reaches 75 °C, proceed to the next step);

[0232] (c)Uniformly drop the remaining vinyl acetate, ethyl acrylate hydroxy, and azobisisobutyronitrile into the reaction system. While dropping, start to control the temperature of the materials to rise to 84 °C, and control the dropping time to be 6 hours; after the temperature of the materials reaches 84 °C, keep the temperature of the materials during the dropping process stable at 84 °C;

[0233] (d)After the dropping is completed, continue to react at 84 °C for 4 hours, and gradually reduce the rotation speed to 150 rpm;

[0234] (e)After the reaction ends, cool down to 50 °C and discharge the materials;

[0235] (f)Remove the solvent at 85 °C and 0.1 MPa vacuum degree, and then crush to obtain the finished product of vinyl acetate copolymer.

[0236] Perform tests on the conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality of the obtained finished product of vinyl acetate copolymer, and the test results are shown in Table 1.

[0237] Comparative Example 1

[0238] A vinyl acetate copolymer, and the weight ratio of its raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0239] The preparation method comprises the following steps:

[0240] (a)Start the stirring of the deoxygenated reaction kettle, and add methanol with a 100% feeding amount, vinyl acetate with a 15% feeding amount, butyl acrylate hydroxy with a 0% feeding amount, azobisisobutyronitrile with a 15% feeding amount, and mercaptoethanol with a 15% feeding amount into the closed polymerization reaction kettle;

[0241] (b)Under stirring, raise the temperature of the materials to 75 °C, and maintain the reaction at 75 °C for 15 minutes;

[0242] (c) The remaining vinyl acetate, butyl acrylate, azobisisobutyronitrile, and mercaptoethanol were uniformly added dropwise to the reaction system. While adding dropwise, the temperature of the material was controlled to rise to 80 °C, and the dropping time was controlled within 6 h. After the material temperature reached 80 °C, the temperature of the material during the dropping process was stabilized at 80 °C.

[0243] (d) After the dropping was completed, the reaction continued at 80 °C for 4 h, and the rotation speed was gradually reduced to 50 rpm.

[0244] (e) After the reaction ended, the temperature was lowered to 50 °C for discharging.

[0245] (f) After removing the solvent under a vacuum of 68 °C and 0.06 MPa, it was crushed to obtain the finished product of vinyl acetate copolymer.

[0246] The obtained finished product of vinyl acetate copolymer was subjected to tests on conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality. The test results are shown in Table 1.

[0247] Comparative Example 2

[0248] A vinyl acetate copolymer, in which the weight ratio of the raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:0:0.175:1.

[0249] Its preparation method includes the following steps:

[0250] (a) Start the stirring of the deoxygenated reaction kettle, and add 100% of the feeding amount of methanol, 15% of the feeding amount of vinyl acetate, 15% of the feeding amount of azobisisobutyronitrile, and 15% of the feeding amount of mercaptoethanol to the closed polymerization reaction kettle.

[0251] (b) Under stirring, raise the temperature of the material to 63 °C. After the temperature reaches 63 °C, start timing, and react the raw materials for 45 min. At the same time, control the temperature of the material to be 75 °C at the 30th min (for the remaining 15 min, maintain the temperature of the material at 75 °C for the reaction).

[0252] (c) The remaining vinyl acetate, azobisisobutyronitrile, and mercaptoethanol were uniformly added dropwise to the reaction system. While adding dropwise, the temperature of the material was controlled to rise to 80 °C, and the dropping time was controlled within 6 h. After the material temperature reached 80 °C, the temperature of the material during the dropping process was stabilized at 80 °C.

[0253] (d) After the dropping was completed, the reaction continued at 80 °C for 4 h, and the rotation speed was gradually reduced to 50 rpm.

[0254] (e) After the reaction ended, the temperature was lowered to 50 °C for discharging.

[0255] (f)The vinyl acetate copolymer finished product is obtained by removing the solvent at 68 °C and a vacuum of 0.06 MPa and then crushing.

[0256] The obtained vinyl acetate copolymer finished product is tested for conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0257] Comparative Example 3

[0258] A vinyl acetate copolymer, in which the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0259] Its preparation method includes the following steps:

[0260] (a)Start the stirring of the deoxygenated reaction kettle, and add 100% feed amount of methanol, 100% feed amount of vinyl acetate, 0% feed amount of butyl hydroxyacrylate, 15% feed amount of azobisisobutyronitrile, and 15% feed amount of mercaptoethanol to the closed polymerization reaction kettle;

[0261] (b)Under stirring, raise the material temperature to 63 °C. After the temperature reaches 63 °C, start timing, and react the raw materials for 45 min. At the same time, control the material temperature to be 75 °C at the 30th min (for the remaining 15 min, maintain the material temperature at 75 °C for reaction);

[0262] (c)Drop the remaining butyl hydroxyacrylate, azobisisobutyronitrile, and mercaptoethanol into the reaction system at a uniform speed. While dropping, start to control the material temperature to rise to 80 °C, and the dropping time is controlled within 6 h; after the material temperature reaches 80 °C, stabilize the material temperature during the dropping process at 80 °C;

[0263] (d)After the dropping is completed, continue to react at 80 °C for 4 h, and gradually reduce the rotation speed to 50 rpm;

[0264] (e)After the reaction ends, cool down to 50 °C and discharge the material;

[0265] (f)The vinyl acetate copolymer finished product is obtained by removing the solvent at 68 °C and a vacuum of 0.06 MPa and then crushing.

[0266] The obtained vinyl acetate copolymer finished product is tested for conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality, and the test results are shown in Table 1.

[0267] Comparative Example 4

[0268] A vinyl acetate copolymer, in which the weight ratio of raw material solvent, vinyl acetate, comonomer, initiator, and chain regulator is 20:100:8.15:0.175:1.

[0269] Its preparation method comprises the following steps:

[0270] (a) Start the stirring of the deoxygenated reaction kettle, and add methanol with a 100% feeding amount, vinyl acetate with a 15% feeding amount, butyl hydroxyacrylate with a 0% feeding amount, azobisisobutyronitrile with a 100% feeding amount, and mercaptoethanol with a 15% feeding amount into the closed polymerization reaction kettle;

[0271] (b) Under stirring, raise the temperature of the materials to 63 °C. Start timing after the temperature reaches 63 °C, and react the raw materials for 45 min. At the same time, control the temperature of the materials to be 75 °C at the 30th min (for the remaining 15 min, maintain the temperature of the materials at 75 °C for the reaction);

[0272] (c) Uniformly drop the remaining vinyl acetate, butyl hydroxyacrylate, and mercaptoethanol into the reaction system. While dropping, start to control the temperature of the materials to rise to 80 °C, and control the dropping time to be 6 h; after the temperature of the materials reaches 80 °C, stabilize the temperature of the materials during the dropping process at 80 °C;

[0273] (d) After the dropping is completed, continue to react at 80 °C for 4 h, and gradually reduce the rotation speed to 50 rpm;

[0274] (e) After the reaction is completed, cool down to 50 °C and discharge the material;

[0275] (f) Remove the solvent at 68 °C and a vacuum degree of 0.06 MPa, and then crush to obtain the finished product of vinyl acetate copolymer.

[0276] Carry out tests on the conversion rate, melt viscosity at 120 °C, GPC value, K value, and hydroxyl functionality of the obtained finished product of vinyl acetate copolymer, and the test results are shown in Table 1.

[0277] Table 1: Performance test results of vinyl acetate copolymer

[0278]

[0279] As can be seen from Table 1, by regulating the feeding ratio, feeding method, reaction temperature and time, and heating rate, etc., the present invention prepares vinyl acetate copolymers with different viscosity numbers, and can realize the wide application of vinyl acetate copolymer resin in the field of adhesives; in addition, by regulating the dosage of the comonomer, vinyl acetate copolymers with different functionalities are prepared, further broadening the application space of this type of adhesive.

[0280] The present invention conducts application tests on the vinyl acetate copolymers of some embodiments as the binder for P2 standard particleboard, and the test results are shown in Table 2.

[0281] Table 2: Application test results of vinyl acetate copolymer

[0282]

[0283] As can be seen from Table 2, the vinyl acetate copolymers with different molecular weights, viscosities, and functionalities prepared by the present invention through regulating the polymerization process exhibit excellent properties in terms of modulus of rupture, modulus of elasticity, water absorption expansion rate, etc. in the particleboard binder.

[0284] In summary, the present invention introduces active groups such as hydroxyl groups, epoxy groups, or amine groups onto the polymer molecular chain of polyvinyl acetate through copolymerization, and prepares vinyl acetate copolymers with different viscosity numbers and good comprehensive properties by regulating the feeding ratio, feeding mode, reaction temperature and time, and heating rate, etc., which can realize the wide application of vinyl acetate copolymer resins in the field of adhesives; in addition, by regulating the dosage of the comonomer, vinyl acetate copolymers with different functionalities are prepared, further broadening the application space of this type of adhesive.

[0285] The above specific embodiments have described the implementation of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple variations all belong to the protection scope of the present invention.

Claims

1. A method for preparing a vinyl acetate copolymer, characterized in that: The following steps are involved: (1) uniformly mixing raw materials including 100% of a solvent, 5%-50% of vinyl acetate, 0-100% of a comonomer, 5%-50% of an initiator, and 0-100% of a chain regulator; wherein the comonomer is an olefinic monomer containing at least one functional group selected from the group consisting of a hydroxyl group, an epoxy group, and an amino group; (2) Raising the material temperature to temperature I, starting the timing after the temperature reaches temperature I, reacting the raw materials for 15-120 min, and controlling the material temperature to be temperature II at the 15-120 min; the temperature II is: 5-45 °C higher than temperature I; (3) Add the remaining vinyl acetate, comonomer, initiator, and chain regulator dropwise to the reaction system, and control the material temperature to rise to temperature III while adding dropwise; the temperature III is: 0-60°C higher than temperature II; (4) After the addition is completed, continue the reaction at temperature III for a period of time and gradually reduce the speed; (5) After the reaction is completed, the temperature is lowered and the material is discharged to obtain a vinyl acetate copolymer.

2. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: In step (2), the temperature I is 30-120 °C.

3. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: The weight ratio of the solvent, vinyl acetate, comonomer, initiator and chain regulator is (5-200):100:(2.5-50):(0.05-0.5):(0-5).

4. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: The comonomer includes but is not limited to at least one of hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, hydroxypentyl acrylate, isopentyl hydroxyacrylate, hydroxyethyl methacrylate, hydroxybutyl methacrylate, hydroxypropyl methacrylate, hydroxypentyl methacrylate, hydroxyphenyl acrylate, hydroxyphenyl methacrylate, tert-butyl hydroxymethacrylate, trimethylolpropane acrylate, hydroxyethyl methacrylate phosphate, hydroxyethyl caprolactone acrylate, 4-hydroxycyclohexyl methacrylate, N-hydroxymethyl acrylamide, acrylamide, N-butoxymethyl (meth) acrylamide, ethyl-3-aminobutyrate, 3-aminoacrylate, epoxy acrylate, epoxy methacrylate, bisphenol A epoxy acrylate, 3,4-epoxycyclohexyl methyl methacrylate, and epoxy propylene acrylate.

5. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: In step (4), after the dropwise addition is completed, the reaction is continued at temperature III for 1-6 h.

6. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: The initiator includes but is not limited to at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di(3,5,6-trimethylhexanoyl) peroxide, tert-butyl peroxypivalate, isopropyl peroxypivalate, tert-butyl peroxypivalate, di(2-ethylhexyl) peroxydicarbonate, dimethyl azobisisobutyrate, azoisobutylcyanamide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxide, and di-tert-butyl peroxide.

7. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: The chain regulator includes but is not limited to a chain transfer agent and / or a chain extender; wherein the chain transfer agent includes but is not limited to at least one of dimercaptoethanol, methyl mercaptan, ethyl mercaptan, acetaldehyde, dodecyl mercaptan, carbon tetrachloride, dichloromethane, n-butyl mercaptan, and octyl mercaptan; the chain extender includes but is not limited to at least one of ethylenediamine, N-isopropylethylenediamine, triethylenetetramine, diethylenetriamine, diphenylmethanediisocyanate, dimethylthiotoluene diamine, 1,4-butanediol, neopentyl glycol, sorbitol, diethylene glycol, triethylene glycol, trimethylolpropane, diethylaminoethanol, and N,N-dihydroxy(diisopropyl)aniline.

8. The method for preparing a vinyl acetate copolymer according to claim 1, characterized in that: The solvent includes, but is not limited to, at least one of isopropanol, methanol, ethanol, n-butanol, acetone, ethyl acetate, methyl acetate, butyl acetate, benzene, toluene, chloroform, and carbon tetrachloride.

9. The vinyl acetate copolymer prepared by the method according to any one of claims 1 to 8.

10. Use of the vinyl acetate copolymer according to claim 9 in the field of adhesives.

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