A waterborne polyurethane, preparation method thereof, and application in photosensitive dry film

Abstract

The present invention provides a waterborne polyurethane and its preparation method and application. The preparation method uses oligomeric diols, diisocyanates and chain extenders as raw materials, and synthesizes a series of waterborne polyurethane resins with adjustable performance by controlling chain extension parameters, hard segment content and hydrophilic monomer content. The present invention also provides a waterborne polyurethane-acrylate core-shell emulsion, which comprises an aqueous phase and latex particles with a core-shell structure, wherein the shell of the core-shell structure is the waterborne polyurethane of the present invention, and the core is an acrylate compound. The emulsion is combined with functional substances such as a photoinitiator, and is evenly coated and dried to form a film to prepare a photosensitive dry film. The photosensitive dry film has the characteristics of good flexibility and strong adhesion, and the preparation process greatly reduces the use of organic solvents, which not only saves resources but also avoids production process safety and environmental protection issues.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and particularly relates to a waterborne polyurethane and a preparation method thereof, and application of the waterborne polyurethane in a photosensitive dry film. Background Art

[0002] The photoresist film, also known as the photosensitive layer, is the most important component of the photosensitive dry film. It undergoes a chemical reaction under the irradiation of a light source of a certain wavelength, causing its solubility to change. The composition of the photoresist mainly includes a main resin, a reactive diluent, a solvent, a photoinitiator, and other additives. Among them, the main resin, as the skeleton, has a key influence on the performance of the photosensitive dry film. It should meet the following conditions: (1) good compatibility with other components in the film; (2) good transmittance in the ultraviolet light region after film formation; (3) good film-forming properties of the composition; and (4) good adhesion and developability after film formation.

[0003] At present, the polymers used in the main resin of photoresist film mainly include (meth)acrylate polymers, norbornene polymers, cycloolefin-maleic anhydride copolymers, etc. Most of them adopt free radical solution polymerization, resulting in the use of large amounts of organic solvents, bringing about problems such as resource waste and environmental pollution, and there are many inconveniences and safety hazards in subsequent storage, transportation and use.

[0004] In recent years, as people's awareness of environmental protection and safety continues to increase, the photosensitive dry film industry has paid more and more attention to the development direction of water-based products.

[0005] In the article "Preparation and Performance Study of Waterborne Acrylic Alkyd UV Photoresist" (Adhesion, 2021, 46(06):1-4), the authors used soybean oil, trimethylolpropane, maleic anhydride, and trimellitic anhydride as the main raw materials to synthesize waterborne alkyd resin, and then added ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, benzophenone, and benzoin ethyl ether to prepare UV-curable waterborne photoresist. This photoresist uses water as a solvent, is safe and environmentally friendly, and has good adhesion to quartz glass or aluminum foil, but there are problems such as uneven mixing of active monomers and the main resin and slow curing.

[0006] Patent CN 1249525C provides a new negative aqueous photoresist composition comprising a polyvinyl acetal polymer, a water-soluble photoactive compound and a crosslinking agent. The composition has good water solubility and can avoid the use of large amounts of organic solvents during use and development.

[0007] In the article “Synthesis and properties of UV-curable hyper branched polyurethane and its application in the negative-type photoresist” (Journal of Wuhan University of Technology, 2014, 29(1): 208-212), Liu et al. used polyethylene glycol, isophorone diisocyanate, diethanolamine and dihydroxymethylpropionic acid as raw materials to synthesize carboxyl-containing UV-curable hyperbranched polyurethane, and used it as a negative photoresist for printed circuit boards. The resolution of the photoresist reached 10 microns, but the contrast was low.

[0008] In summary, water-based photosensitive dry film is safe, environmentally friendly, resource-saving and has huge social benefits. However, related technologies and engineering issues, especially the development of the main resin, still need further in-depth research. Summary of the Invention

[0009] Therefore, the purpose of the present invention is to provide a new main resin for water-based photosensitive dry film and its preparation method and application. The photosensitive dry film prepared using this resin has good flexibility and strong adhesion, can be stored and transported at room temperature, and is easy to use.

[0010] The purpose of the present invention is achieved through the following technical solutions.

[0011] The first aspect of the present invention provides an aqueous polyurethane used as a main resin of a photosensitive dry film, wherein the aqueous polyurethane has a structure as shown in formula (I):

[0012]

[0013] Among them, 1≤n≤50,

[0014] R2 and R4 are independently selected from One of the following;

[0015] One of R1 and R5 is selected from One of the first chain extension units, the other of which is selected from One of the second chain extension units;

[0016] R3 is wherein each m is independently an integer of 2 to 25.

[0017] According to the waterborne polyurethane provided by the present invention, the sum of the mass of the first chain extension unit and the second chain extension unit accounts for 5-25% of the total mass of the waterborne polyurethane, preferably 10-20%, and most preferably 15%.

[0018] Preferably, the first chain extension unit accounts for 4 to 14% of the total mass of the waterborne polyurethane; and the second chain extension unit accounts for 1 to 11% of the total mass of the waterborne polyurethane.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned waterborne polyurethane used as the main resin of the photosensitive dry film, the preparation method comprising the following steps:

[0020] S1: A polyurethane prepolymer is obtained by reacting an oligomer diol having a molecular weight of 400 to 5000 with a diisocyanate;

[0021] S2: using a first chain extender and a second chain extender in the presence of a catalyst to chain extend the polyurethane prepolymer to obtain the waterborne polyurethane,

[0022] The first chain extender is used to form the first chain extender unit; the second chain extender is used to form the second chain extender unit.

[0023] According to the preparation method provided by the present invention, the diisocyanate can be selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, cyclohexane diisocyanate, cyclohexane dimethylene diisocyanate, hexamethylene diisocyanate and dicyclohexylmethane diisocyanate.

[0024] The first chain extender may be selected from one of dimethylol propionic acid, dimethylol butyric acid and sodium 1,4-butanediol-2-sulfonate.

[0025] The second chain extender may be selected from one of 1,4-butanediol, ethylene glycol, diethylene glycol, 1,6-hexanediol, hydroquinone dihydroxyethyl ether and resorcinol dihydroxyethyl ether.

[0026] The oligomer diol may be selected from one or more of polytetramethylene glycol, polypropylene glycol, polyethylene glycol, polycaprolactone diol, polyethylene adipate glycol and polybutylene adipate glycol.

[0027] According to the preparation method provided by the present invention, the temperature of the addition reaction in step S1 is preferably 65-85°C, and the time is preferably 2-4 hours. Preferably, the end point of the addition reaction in step S1 is when the hydroxyl content in the reaction system is approximately 0.

[0028] According to the preparation method provided by the present invention, step S2 may include: reacting the polyurethane prepolymer prepared in step S1 with the first chain extender and the second chain extender at 65-85° C. for 1-2 hours, adding a catalyst, and then continuing the reaction at 65-85° C. for 1-2 hours to chain extend the polyurethane prepolymer.

[0029] Preferably, the end point of the chain extension reaction in step S2 is when the isocyanate content in the reaction system is approximately 0.

[0030] Preferably, the catalyst used in step S2 is di-n-butyltin dilaurate.

[0031] Preferably, the total mass of the first chain extender and the second chain extender added is 4-15% of the mass of the polyurethane prepolymer.

[0032] In the present invention, for the convenience of description, the relationship between the addition amounts of various raw materials is referred to as "material parameters".

[0033] In a preferred embodiment of the present invention, the addition amounts of the oligomer diol, the first chain extender, the second chain extender and the diisocyanate meet the following three conditions:

[0034] (1)

[0035] Among them, R T is the chain extension parameter, n (-NCO) is the amount (in moles) of isocyanate in the diisocyanate, n (-OH) is the total amount (in moles) of hydroxyl groups in the oligomer diol, the first chain extender, and the second chain extender;

[0036] (2)

[0037] Among them, H represents the hard segment content, m (二异氰酸酯) is the mass of diisocyanate, m (扩链剂) is the sum of the mass of the first chain extender and the second chain extender, m (低聚物二元醇) is the mass of the oligomer diol;

[0038] (3)

[0039] Among them, ω (亲水单体) Represents the hydrophilic monomer content, m (第一扩链剂) is the mass of the first chain extender; m (扩链剂) is the sum of the mass of the first chain extender and the second chain extender, m (二异氰酸酯) is the mass of diisocyanate, m (低聚物二元醇) is the mass of the oligomer diol.

[0040] The third aspect of the present invention provides an aqueous polyurethane-acrylate core-shell emulsion, which comprises an aqueous phase and latex particles, wherein the latex particles have a core-shell structure, the outer shell of the core-shell structure is the aqueous polyurethane provided by the first aspect of the present invention, and the inner core of the core-shell structure is an acrylate compound.

[0041] According to the emulsion provided by the present invention, the acrylate compound may be one or more of ethyl acrylate, butyl acrylate, methyl acrylate, methyl methacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, epoxy resin diacrylate, pentaerythritol triacrylate, trimethylolpropane triethylene ester and trihydroxypropane tetraacrylate.

[0042] Preferably, the mass ratio of the outer shell to the inner core of the core-shell structure is 1:0.5-1.

[0043] In a preferred embodiment of the present invention, the mass ratio of the water phase to the latex particles in the emulsion is 1:0.5-0.8.

[0044] According to the emulsion provided by the present invention, the aqueous phase is a dispersion medium, and preferably, the dispersion medium is water.

[0045] The fourth aspect of the present invention provides a method for preparing the above-mentioned emulsion, which comprises: preparing a water-based polyurethane according to the method for preparing a water-based polyurethane provided in the second aspect of the present invention, wherein, during the chain extension reaction in step S2, an acrylate monomer is added to the chain extension reaction system, and then neutralized into a salt and stirred and emulsified with water to obtain the water-based polyurethane-acrylate core-shell emulsion.

[0046] Since the viscosity of the reactants increases dramatically during the chain extension reaction, the present invention creatively adds an acrylate monomer to the chain extension reaction system, which serves as a solvent to reduce the viscosity of the reaction system and to form the core of the core-shell structure.

[0047] According to the emulsion preparation method provided by the present invention, the acrylate monomer includes one or more of a monofunctional reactive diluent, a difunctional reactive diluent, a trifunctional reactive diluent and a tetrafunctional reactive diluent.

[0048] Wherein, the monofunctional reactive diluent may include ethyl acrylate, butyl acrylate, methyl acrylate and / or methyl methacrylate;

[0049] The bifunctional reactive diluent may include dipropylene glycol diacrylate, tripropylene glycol diacrylate and / or epoxy resin diacrylate;

[0050] The trifunctional reactive diluent may include pentaerythritol triacrylate and / or trimethylolpropane triethylene ester;

[0051] The tetrafunctional reactive diluent may include trihydroxypropane tetraacrylate.

[0052] The salt-forming agent used in the neutralization and salt formation may include triethylamine.

[0053] Preferably, the temperature for the neutralization to form salt is 30-50° C., the time is 10-30 min, and the time for the water-adding emulsification can be 10-30 min.

[0054] The fifth aspect of the present invention further provides the use of the aqueous polyurethane-acrylate core-shell emulsion as a precursor liquid for a photosensitive dry film.

[0055] In a preferred embodiment, the application includes: adding a photoinitiator to the aqueous polyurethane-acrylate core-shell emulsion, and then coating and drying to obtain a photosensitive dry film.

[0056] Preferably, the photoinitiator may be 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone and / or 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone;

[0057] Preferably, the coating thickness is 20-100 μm, and the drying temperature is 40-70°C.

[0058] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0059] (1) The water-based polyurethane and its preparation method provided by the present invention use oligomer diol, diisocyanate and chain extender as raw materials, and control the chain extension parameter (R T ), hard segment content (H) and hydrophilic monomer content (ω (亲水单体) ) and other material parameters, which can not only flexibly adjust the resin molecular weight and rigid structure content to optimize the mechanical properties of the resin, but also control the amount of carboxyl groups introduced by adjusting the hydrophilic monomer content, thereby controlling the alkali washing efficiency.

[0060] (2) The emulsion provided by the present invention is an aqueous polyurethane-acrylate core-shell structure water-in-oil emulsion. During its preparation process, acrylate monomers are used to replace organic solvents to reduce the viscosity of the reactants, thereby greatly reducing the use of organic solvents, which is in line with people's current and future concepts of resource conservation and environmental protection.

[0061] (3) The aqueous polyurethane-acrylate core-shell emulsion provided by the present invention is used as a photosensitive dry film precursor, which has the characteristics of strong stability, good storage properties, and safe transportation. In addition, during use, no organic solvent is volatilized, thereby avoiding environmental pollution and health hazards to operators.

[0062] (4) The photosensitive dry film prepared by using the emulsion provided by the present invention has the characteristics of good flexibility and strong adhesion, and the dry film can be stored and transported at room temperature, is convenient for direct use, and can greatly improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

[0064] Figure 1 This is a comparison chart of infrared spectra of the reaction raw materials and products in Example 1 of the present invention;

[0065] Figure 2 This is a comparison chart of infrared spectra of the waterborne polyurethane (main resin), the soft photosensitive dry film (soft film), and the hard photosensitive dry film (hard film) prepared in Example 9 of the present invention. DETAILED DESCRIPTION

[0066] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for illustrating the present invention, not for limiting the scope of the present invention.

[0067] The present invention provides a waterborne polyurethane, a preparation method, and an application thereof. The preparation method uses oligomeric diols, diisocyanates, and chain extenders as raw materials, and can synthesize a series of waterborne polyurethane resins with adjustable performance by controlling material parameters. Specifically:

[0068] (1) By controlling the chain extension parameter (R T ) to adjust the molecular weight of the resin. The molecular weight of polyurethane affects the properties of the photosensitive dry film. When the molecular weight is large, the thermal stability and corrosion resistance of the photosensitive dry film are increased. When the molecular weight is small, the adhesion between the photosensitive dry film and the substrate is improved. Chain extension parameter R T The closer it is to 1, the larger the molecular weight, the stronger the interaction between molecules, and the better the mechanical properties.

[0069] (2) Optimize mechanical properties by controlling the hard segment content (H). The higher the hard segment content H, the more rigid the structure and the higher the glass transition temperature.

[0070] (3) By controlling the hydrophilic monomer content (ω 亲水单体 ) to change the acidity of the resin and thus optimize the alkaline washing performance.

[0071] The present invention also provides a waterborne polyurethane-acrylate core-shell emulsion. Common waterborne polyurethane-acrylate emulsions are synthesized by attaching an acrylate monomer to the end of a waterborne polyurethane. After film formation, this structured emulsion has few photocurable groups, low photocuring activity, and a low crosslinking density. The waterborne polyurethane-acrylate core-shell emulsion provided by the present invention, however, leverages the hydrophilic self-emulsifying properties of the waterborne polyurethane to de-emulsify the encapsulated hydrophobic acrylate monomer during hydration, forming a stable core-shell emulsion. Furthermore, after adding a photoinitiator, it rapidly crosslinks under ultraviolet light, resulting in a significant difference in alkali solubility before and after exposure.

[0072] The present invention also provides a method for preparing the above-mentioned aqueous polyurethane-acrylate core-shell emulsion. The difference from the existing emulsion preparation method is that the viscosity of the reaction system will increase during the chain extension process of preparing aqueous polyurethane. At this time, the addition of acrylate monomers instead of solvents reduces the viscosity of the reaction system, ensuring that the subsequent chain extension and neutralization reactions proceed smoothly. During the further addition of water and mixing, due to the presence of polyurethane, the neutralized carboxyl groups have excellent hydrophilicity and will self-emulsify into large molecular coil micelles, while the hydrophobic acrylate monomers will spontaneously be emulsified in the aqueous polyurethane micelles, forming a core-shell emulsion with aqueous polyurethane as the shell and acrylate monomers as the core. The addition amount satisfies the following relationship:

[0073] m 聚氨酯 :m 丙烯酸酯单体 =1:0.5~1.0.

[0074] The present invention also provides the use of the aqueous polyurethane-acrylate core-shell emulsion as a photosensitive dry film precursor. The aqueous polyurethane-acrylate core-shell emulsion has strong stability, thus providing excellent storage properties and safe transportation. During use, no organic solvent volatilization occurs, thus avoiding environmental pollution and health hazards to operators.

[0075] Compared to traditional photosensitive dry film preparation methods, the photosensitive dry film provided by the present invention, using the water-based polyurethane as the main resin, exhibits excellent mechanical properties and strong adhesion. Furthermore, a hydrophilic chain extender allows the introduction of a large number of hydrophilic groups, and controlled neutralization ensures the resin's water solubility while retaining a large number of carboxyl groups for subsequent alkali washability. Furthermore, the resulting photosensitive dry film is transparent and uniform, exhibits good transmittance in the ultraviolet region, and exhibits excellent mechanical properties at room temperature, making it easy to transport and use directly.

[0076] The test standards of the test parameters of the present invention are as follows:

[0077] Determination of isocyanate content: Referring to ISO14896-2009, the di-n-butylamine method was adopted, and the excess di-n-butylamine was titrated with hydrochloric acid to determine the isocyanate content in the system.

[0078] Material mechanical properties test: Referring to ISO37-2017, the samples were made into standard specimens, and the tensile strength (σ) and elongation at break (ε) of the materials were tested at a tensile rate of 100 mm / min.

[0079] Fourier transform infrared spectroscopy analysis: Rayleigh WQF-530 infrared spectrometer was used for testing. The liquid was prepared by film coating method, and the thin film was tested by attenuated total reflection.

[0080] Molecular weight test: Waters gel permeation chromatography was used to determine the molecular weight and molecular weight distribution of the resin.

[0081] Adhesion test: Refer to GBT9286-1998 and use the cross-cut method to test the adhesion of the sample.

[0082] Thermogravimetric analysis: Thermogravimetric analysis of the samples was performed using a STA PC / H synchronous thermal analyzer.

[0083] Glass transition temperature test: The glass transition temperature of the samples was analyzed using a TA Q800 dynamic thermomechanical analyzer.

[0084] Hereinafter, the waterborne polyurethane of the present invention was prepared through Examples 1-8, a waterborne polyurethane emulsion was prepared using the prepared waterborne polyurethane, and then a photosensitive dry film was prepared using the emulsion, and structural characterization and performance testing were performed.

[0085] Example 1

[0086] The specific steps are as follows:

[0087] (1) 20 g of polytetrahydrofuran diol (molecular weight Mn=2000) and 7.24 g of toluene diisocyanate were added to a reaction flask and reacted at 80° C. for 2 hours to obtain a polyurethane prepolymer.

[0088] (2) Weigh 1.85 g of dihydroxymethylpropionic acid and add it to the reaction bottle of step (1). After reacting for 2 hours, add 0.01% of the total weight of di-n-butyltin dilaurate and 1.68 g of 1,4-butanediol, and continue to react for 2 hours (during which time acetone is added appropriately according to the viscosity change to avoid the reaction from being unable to proceed normally due to excessive reaction viscosity).

[0089] (3) The reaction system was cooled to 40° C., 1.40 g of triethylamine was weighed and added to the reaction flask. After neutralization for 15 minutes, 75.06 g of deionized water (added based on a solid content of 30%) was added to obtain an aqueous polyurethane emulsion.

[0090] (4) The above emulsion is mixed with 3% of the photoinitiator 2-hydroxy-2-methyl-1-phenylacetone and poured into a polytetrafluoroethylene mold. The mixture is dried in an oven at 70°C to obtain a soft photosensitive dry film. The hard photosensitive dry film is obtained by UV curing.

[0091] After calculation, the material parameters in the above formula are as follows: R T =0.98, H=35%, ω 亲水单体 =6%, m 丙烯酸酯 :m 聚氨酯 =0:1.

[0092] Figure 1 Be the infrared spectrogram comparison diagram of the reaction raw materials and product in the present embodiment, wherein, TDI represents toluene diisocyanate, WPU represents waterborne polyurethane, and PTMG represents polytetramethylene glycol. Figure 1 As shown, the spectral line of PTMG is at 3471cm -1 There is an obvious -OH stretching vibration peak at 2258cm -1 There is an obvious -NCO characteristic absorption peak at 3295cm, while in the infrared spectrum of the product WPU, the -NCO characteristic absorption peak disappears. -1 、1724cm -1 and 1533cm -1 The stretching vibration peak corresponding to -NH-, the C=O stretching vibration peak of carbamate and the deformation vibration peak of -NH- appeared at , indicating that the -NCO in the raw material has been completely reacted and the -NH-COO- group has been generated.

[0093] Example 2

[0094] This example was carried out in the same manner as Example 1, except that the amount of toluene diisocyanate added in step (1) was 7.14 g, the amount of 1,4-butanediol added in step (2) was 1.78 g, and the material parameters were: R T =0.94, H=35%, ω 亲水单体 =6%, m 丙烯酸酯 :m 聚氨酯 =0:1.

[0095] Example 3

[0096] This example was carried out in the same manner as Example 1, except that the amount of toluene diisocyanate added in step (1) was 7.04 g, the amount of 1,4-butanediol added in step (2) was 1.88 g, and the material parameters were: R T =0.90, H=35%, ω 亲水单体 =6%, m 丙烯酸酯 :m聚氨酯 =0:1.

[0097] Example 4

[0098] This example was carried out in the same manner as Example 1, except that the amount of toluene diisocyanate added in step (1) was 6.94 g, the amount of 1,4-butanediol added in step (2) was 1.98 g, and the material parameters were: R T =0.86, H=35%, ω 亲水单体 =6%, m 丙烯酸酯 :m 聚氨酯 =0:1.

[0099] Example 5

[0100] This example was carried out in the same manner as Example 1, except that: in step (1), the amount of toluene diisocyanate added was 4.61 g, the amount of dihydroxymethylpropionic acid added in step (2) was 1.60 g, the amount of 1,4-butanediol added was 0.46 g, the amount of triethylamine added in step (3) was 1.21 g, and the amount of deionized water added was 65.05 g. Material parameters: R T =0.98, H=25%, ω 亲水单体 =6%, m 丙烯酸酯 :m 聚氨酯 =0:1.

[0101] Example 6

[0102] This example was carried out in the same manner as Example 1, except that: in step (1), the amount of toluene diisocyanate added was 10.83 g, the amount of dihydroxymethylpropionic acid added in step (2) was 2.18 g, the amount of 1,4-butanediol added was 1.98 g, the amount of triethylamine added in step (3) was 1.64 g, and the amount of deionized water added was 88.67 g. Material parameters: R T =0.98, H=45%, ω 亲水单体 =6%, m 丙烯酸酯 :m 聚氨酯 =0:1.

[0103] Example 8

[0104] This example was carried out in the same manner as Example 1, except that: in step (1), the amount of toluene diisocyanate added was 8.82 g, the amount of dihydroxymethylpropionic acid added in step (2) was 2.33 g, the amount of 1,4-butanediol added was 2.18 g, the amount of triethylamine added in step (3) was 1.76 g, the amount of deionized water added was 81.88 g, and the material parameters were: R T=0.98, H=40%, ω 亲水单体 =7%, m 丙烯酸酯 :m 聚氨酯 =0:1.

[0105] Characterization and testing

[0106] (1) Similar to Example 1, the infrared spectrum analysis of the products of Examples 2-8 showed that the characteristic absorption peak of -NCO disappeared. At the same time, the peak at 3295 cm -1 、1724cm -1 and 1533cm -1 The stretching vibration peak corresponding to -NH-, the C=O stretching vibration peak of carbamate and the deformation vibration peak of -NH- appeared at , indicating that the -NCO in the raw material has been completely reacted and the -NH-COO- group has been generated.

[0107] (2) The mechanical properties of the materials obtained in Examples 1-8 were tested, and the chain extension parameter R T The results of the effects on the properties of the main resin of the photosensitive dry film are summarized in Table 1.

[0108] Table 1 Chain extension parameters R T Influence on the properties of the main resin of photosensitive dry film

[0109] Example <![CDATA[Chain extension parameter R T > Number average molecular weight Mn Film-forming properties Tensile strengthσ / MPa Elongation at break ε / % 1 0.98 19 800 better 5.71 2620 2 0.94 14 300 generally 1.26 1227 3 0.90 13 300 Poor -- -- 4 0.86 11 600 Difference -- --

[0110] As can be seen from Table 1, as the RT changes from 0.86 to 0.98, its number-average molecular weight increases from 11,600 to 19,800. The main resin's film-forming properties become increasingly better, with increased tensile strength and elongation at break. This is because as the molecular weight increases, the molecular chains become longer, allowing for more hydrogen bonds to form between molecules, resulting in greater cohesion, which is beneficial for film formation and improves tensile strength and elongation at break.

[0111] (III) By comparing the mechanical properties of the materials obtained in Examples 1, 5 and 6, the effect of the hard segment content H on the properties of the main resin of the photosensitive dry film was investigated. The results are shown in Table 2 below.

[0112] Table 2 Effect of hard segment content H on the properties of the main resin of photosensitive dry film

[0113] Example Hard segment content H / % Film-forming properties Tensile strengthσ / MPa Elongation at break ε / % 5 25 generally -- -- 1 35 better 5.71 2620 6 45 good 16.83 806

[0114] As can be seen from Table 2, the tensile strength of the main resin of the photosensitive dry film increases with increasing hard segment content, while the elongation at break gradually decreases with increasing hard segment content. This is because when the hard segment content is low, there are fewer urethane groups in the molecular chain, the interaction between molecules is weak, and it is difficult to form effective physical crosslinks between chains, resulting in low tensile strength and high elongation at break.

[0115] Hereinafter, the waterborne polyurethane of the present invention was prepared by Examples 9-16, the waterborne polyurethane prepared was used to prepare the waterborne polyurethane-acrylate core-shell emulsion of the present invention, and then the emulsion was used to prepare a photosensitive dry film, and the structure characterization and performance testing were carried out.

[0116] Example 9

[0117] This embodiment prepares the waterborne polyurethane of the present invention.

[0118] The specific steps are as follows:

[0119] (1) 20 g of polytetrahydrofuran diol (molecular weight Mn=2000) and 8.82 g of toluene diisocyanate were added to a reaction flask and reacted at 80° C. for 2 hours to obtain a polyurethane prepolymer.

[0120] (2) Weigh 2.33 g of dihydroxymethylpropionic acid and add it to the reaction bottle of step (1). After reacting for 2 hours, add 0.01% of the total mass of di-n-butyltin dilaurate and 2.18 g of 1,4-butanediol. Continue to react for 2 hours. During this period, solvent (or no solvent) and 13.84 g of dipropylene glycol diacrylate are appropriately added according to the change in viscosity to avoid the reaction from being unable to proceed normally due to excessive reaction viscosity.

[0121] (3) The reaction mixture was cooled to 40° C., 1.76 g of triethylamine was weighed and added to the reaction flask. After neutralization for 15 minutes, 81.88 g of deionized water (added at a solid content of 30%) was added to obtain a waterborne polyurethane-acrylate core-shell emulsion.

[0122] (4) The above emulsion is mixed with 3% of the photoinitiator 2-hydroxy-2-methyl-1-phenylacetone and evenly poured into a polytetrafluoroethylene mold and dried in an oven at 70°C to obtain a photosensitive dry film soft film, which is then cured by ultraviolet light to obtain a photosensitive dry film hard film.

[0123] After calculation, the material parameters in the above formula are as follows: R T =0.98, H=40%, ω 亲水单体 =7%, m 丙烯酸酯(二丙二醇二丙稀酸酯) :m 聚氨酯 =0.4:1.

[0124] Figure 2 The infrared spectra of the waterborne polyurethane (main resin), the soft photosensitive dry film (soft film) and the hard photosensitive dry film (hard film) prepared in this embodiment are compared. Figure 2 As shown, the spectrum of the main resin is at 1633cm -1There is no characteristic absorption peak of -C=C-, but after encapsulating the acrylate monomer and emulsifying, the photosensitive dry film soft film (soft film) formed has an obvious peak, and when the photosensitive dry film hard film (hard film) is formed after UV curing, this characteristic peak basically disappears, which indicates that the acrylate monomer is well encapsulated inside the waterborne polyurethane to form a core-shell structure, and when UV curing is used, the monomer is basically reacted completely.

[0125] Example 10

[0126] This example was carried out in the same manner as Example 9, except that the amount of dipropylene glycol diacrylate added in step (2) was 27.68 g, and the material parameters were: T =0.98, H=40%, ω 亲水单体 =7%, m 丙烯酸酯(二丙二醇二丙稀酸酯) :m 聚氨酯 =0.8:1.

[0127] Example 11

[0128] This example was carried out in the same manner as Example 9, except that the amount of dipropylene glycol diacrylate added in step (2) was 41.52 g, and the material parameters were: T =0.98, H=40%, ω 亲水单体 =7%, m 丙烯酸酯(二丙二醇二丙稀酸酯) :m 聚氨酯 =1.2:1.

[0129] Example 12

[0130] This example was carried out in the same manner as Example 9, except that in step (2), 13.84 g of butyl acrylate was used instead of 13.84 g of dipropylene glycol diacrylate. Material parameters: R T =0.98, H=40%, ω 亲水单体 =7%, m 丙烯酸酯(丙烯酸丁酯) :m 聚氨酯 =0.4:1.

[0131] Example 13

[0132] This example was carried out in the same manner as Example 9, except that in step (2), 13.84 g of trimethylolpropane triethylene glycol ester was used instead of 13.84 g of dipropylene glycol diacrylate. Material parameters: R T =0.98, H=40%, ω 亲水单体 =7%, m 丙烯酸酯(三羟甲基丙烷三乙烯酸酯) :m 聚氨酯 =0.4:1.

[0133] Example 14

[0134] This example was carried out in the same manner as Example 9, except that: in step (1), the amount of toluene diisocyanate added was 8.75 g, the amount of dimethylol propionic acid added in step (2) was 2.67 g, the amount of 1,4-butanediol added was 1.92 g, the amount of dipropylene glycol diacrylate added was 26.67 g, the amount of triethylamine added in step (3) was 1.51 g, and the amount of deionized water added was 81.37 g (added at a solid content of 30%). Material parameters: R T =0.98, H=40%, ω 亲水单体 =8%, (neutralized to 6%), m 丙烯酸酯(二丙二醇二丙稀酸酯) :m 聚氨酯 =0.8:1.

[0135] Example 15

[0136] This example was carried out in the same manner as Example 9, except that: in step (1), the amount of toluene diisocyanate added was 8.46 g, the amount of dimethylol propionic acid added in step (2) was 4.00 g, the amount of 1,4-butanediol added was 0.88 g, the amount of dipropylene glycol diacrylate added was 26.67 g, the amount of triethylamine added in step (3) was 1.51 g, and the amount of deionized water added was 81.37 g (added at a solid content of 30%). Material parameters: R T =0.98, H=40%, ω 亲水单体 =12%, (neutralized to 6%), m 丙烯酸酯(二丙二醇二丙稀酸酯) :m 聚氨酯 =0.8:1.

[0137] Example 16

[0138] This example was carried out in the same manner as Example 9, except that: in step (1), the amount of toluene diisocyanate added was 8.24 g, the amount of dimethylol propionic acid added in step (2) was 5.00 g, the amount of 1,4-butanediol added was 0, the amount of dipropylene glycol diacrylate added was 26.67 g, the amount of triethylamine added in step (3) was 1.51 g, and the amount of deionized water added was 81.37 g (added at a solid content of 30%). Material parameters: R T =0.98, H=40%, ω 亲水单体 =15%, (neutralized to 6%), m 丙烯酸酯(二丙二醇二丙稀酸酯) :m 聚氨酯 =0.8:1.

[0139] Characterization and testing

[0140] (1) Similar to Example 9, the infrared spectrum analysis of Examples 10-16 showed that the spectrum line of the main resin was at 1633 cm -1 There is no characteristic absorption peak of -C=C-, but after encapsulating the acrylate monomer and emulsifying, the photosensitive dry film soft film (soft film) formed has an obvious peak, and when the photosensitive dry film hard film (hard film) is formed after UV curing, this characteristic peak basically disappears, which indicates that the acrylate monomer is well encapsulated inside the waterborne polyurethane to form a core-shell structure, and when UV curing is used, the monomer is basically reacted completely.

[0141] (II) Mechanical property testing of the materials prepared in Examples 9-16. By comparing Examples 7 with 9-13, the effects of different types and contents of acrylate on the properties of the photosensitive dry film and the hard film were examined. The results are shown in Table 3. The soft film refers to the dry film before exposure; the hard film refers to the dry film after exposure.

[0142] Table 3 Effect of acrylate on the properties of soft and hard film of photosensitive dry film

[0143]

[0144] *σ: tensile strength, unit: MPa, ε: elongation at break, unit: %, Tg: glass transition temperature

[0145] From the comparison of Example 7, Example 9, Example 10 and Example 11, it can be seen that with the increase of the acrylate monomer content, the tensile strength of the soft photosensitive dry film decreases sharply, the elongation at break first decreases and then increases, and the glass transition temperature gradually decreases. This is because with the addition of the acrylate monomer, it acts as a plasticizer, resulting in a decrease in the interaction force between molecules and facilitating the relative movement of the chains. On the other hand, the tensile strength of the hard photosensitive dry film formed after curing first decreases and then increases, the elongation at break continues to decrease, and the glass transition temperature increases significantly. This is because when the acrylate content in the system is low, the network structure is incomplete and the original crystallinity of PTMG is destroyed, which in turn reduces the tensile strength. With the increase of the acrylate content, the network structure of the system becomes increasingly dense, which increases the tensile strength, but significantly reduces the elongation at break.

[0146] (III) The effects of acrylate monomer type on the properties of the photosensitive dry film were investigated by comparing the properties of the materials prepared in Examples 9, 12, and 13. Different types of acrylate monomers had little effect on the mechanical properties of the soft photosensitive dry film. This is because, given a certain acrylate monomer content, before photocuring, the stretching process primarily reflects the expansion and contraction movement of the main resin under plasticization. After UV curing, as the functionality of the acrylate monomer increases, the tensile strength increases, the elongation at break decreases, and the glass transition temperature increases. This is because the greater the monomer functionality, the higher the chemical crosslink density formed during curing, the denser and more complete the network structure, and the overall material exhibits high strength and hardness.

[0147] (IV) By comparing the properties of the materials obtained in Examples 14, 15 and 16, the effects of different carboxylic acid contents in the main resin on the properties of the photosensitive dry film were investigated. The results are shown in Table 4 below.

[0148] Table 4 Effect of different carboxylic acid contents on photosensitive dry film properties

[0149] Example <![CDATA[ω 亲水单体 / %]]> Neutralization degree / % Adhesion Alkali washing resistance 14 8 75 1 generally 15 12 50 1 better 16 15 40 1 good

[0150] From the comparison of Example 14, Example 15 and Example 16, it can be seen that by changing the hydrophilic monomer content and neutralization degree of the main resin to adjust the residual hydrophilic group (-COOH) content in the dry film, the alkali washability of the dry film can be effectively changed, and the higher the residual group content, the better the alkali washing effect.

[0151] The contents illustrated in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications of the present invention by those skilled in the art shall fall within the scope defined by the claims attached to this application.

Claims

1. A waterborne polyurethane-acrylate core-shell emulsion for preparing a photosensitive dry film, the emulsion comprising an aqueous phase and latex particles, wherein: The latex particles have a core-shell structure, the shell of the core-shell structure is a waterborne polyurethane used as a main resin, and the core of the core-shell structure is an acrylate compound used as a photosensitive monomer, wherein the waterborne polyurethane has a structure as shown in formula (I): （I） Among them, 1≤n≤50, R2 and R4 are independently selected from 、 、 、 、 、 、 、 、 or One of the following; One of R1 and R5 is selected from 、 and One of the first chain extension units, the other of which is selected from 、 、 、 、 and One of the second chain extension units; R3 is 、 、 、 、 or wherein each m is independently an integer of 2 to 25.

2. The emulsion according to claim 1, wherein the sum of the masses of the first chain extension unit and the second chain extension unit accounts for 5 to 25% of the total mass of the aqueous polyurethane.

3. The emulsion according to claim 2, wherein the sum of the masses of the first chain extension unit and the second chain extension unit accounts for 10 to 20% of the total mass of the waterborne polyurethane.

4. The emulsion according to claim 3, wherein the sum of the masses of the first chain extension unit and the second chain extension unit accounts for 15% of the total mass of the waterborne polyurethane.

5. The emulsion according to any one of claims 1 to 4, wherein The first chain extension unit accounts for 4-14% of the total mass of the waterborne polyurethane; the second chain extension unit accounts for 1-11% of the total mass of the waterborne polyurethane.

6. The emulsion according to claim 1, wherein The acrylate compound is selected from one or more of ethyl acrylate, butyl acrylate, methyl acrylate, methyl methacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, epoxy resin diacrylate and trimethylolpropane triethylene ester.

7. The emulsion according to claim 1, wherein The mass ratio of the outer shell to the inner core of the core-shell structure is 1:0.5-1.

8. The emulsion according to claim 1, wherein The mass ratio of the water phase to the latex particles in the emulsion is 1:0.5-0.

8.

9. A method for preparing the aqueous polyurethane-acrylate core-shell emulsion according to any one of claims 1 to 8, comprising the steps of: S1: A polyurethane prepolymer is obtained by reacting an oligomer diol with a molecular weight of 400 to 5000 with a diisocyanate; S2: using a first chain extender and a second chain extender in the presence of a catalyst to chain extend the polyurethane prepolymer to obtain the waterborne polyurethane; during the chain extension reaction, adding an acrylate monomer to the chain extension reaction system, neutralizing it to form a salt, and adding water for stirring and emulsification to obtain the waterborne polyurethane-acrylate core-shell emulsion; in, The first chain extender is used to form the first chain extender unit; the second chain extender is used to form the second chain extender unit.

10. The preparation method according to claim 9, wherein The diisocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, phenylene diisocyanate, cyclohexane diisocyanate, cyclohexane dimethylene diisocyanate, hexamethylene diisocyanate and dicyclohexylmethane diisocyanate.

11. The preparation method according to claim 9, wherein The first chain extender is selected from one of dimethylol propionic acid, dimethylol butyric acid and 1,4-butanediol-2-sulfonate sodium; The second chain extender is selected from one of 1,4-butanediol, ethylene glycol, diethylene glycol, 1,6-hexanediol, hydroquinone dihydroxyethyl ether and resorcinol dihydroxyethyl ether.

12. The preparation method according to claim 9, wherein The oligomer diol is selected from one or more of polytetramethylene glycol, polypropylene glycol, polyethylene glycol, polycaprolactone glycol, polyethylene adipate glycol and polybutylene adipate glycol.

13. The preparation method according to claim 9, wherein The temperature of the addition reaction in step S1 is 65-85° C., and the time is 2-4 hours.

14. The preparation method according to claim 9, wherein The end point of the addition reaction in step S1 is when the hydroxyl content in the reaction system is 0.

15. The preparation method according to claim 9, wherein The step S2 comprises: reacting the polyurethane prepolymer prepared in step S1 with the first chain extender and the second chain extender at 65-85° C. for 1-2 hours, adding a catalyst, and then continuing the reaction at 65-85° C. for 1-2 hours to chain extend the polyurethane prepolymer.

16. The preparation method according to claim 9, wherein The end point of the chain extension reaction in step S2 is when the content of isocyanate in the reaction system is 0.

17. The preparation method according to claim 9, wherein The catalyst used in step S2 is di-n-butyltin dilaurate.

18. The preparation method according to claim 9, wherein The total mass of the first chain extender and the second chain extender added is 4-15% of the mass of the polyurethane prepolymer.

19. The preparation method according to any one of claims 9 to 18, wherein The addition amounts of the oligomer diol, the first chain extender, the second chain extender and the diisocyanate meet the following three conditions: （1） Among them, R T is the chain extension parameter, n （-NCO) is the amount of isocyanate in the diisocyanate, n （-OH) is the total amount of hydroxyl groups in the oligomer diol, the first chain extender, and the second chain extender; （2） Among them, H represents the content of hard segment, m （二异氰酸酯） is the mass of diisocyanate, m （扩链剂） is the sum of the mass of the first chain extender and the second chain extender, m （低聚物二元醇） is the mass of the oligomer diol; （3） Among them, ω （亲水单体） Represents the content of hydrophilic monomer, m （第一扩链剂） is the mass of the first chain extender; m （扩链剂） is the sum of the mass of the first chain extender and the second chain extender, m （二异氰酸酯） is the mass of diisocyanate, m （低聚物二元醇） is the mass of the oligomer diol.

20. The preparation method according to claim 9, wherein The acrylate monomer includes one or more of a monofunctional reactive diluent, a difunctional reactive diluent, a trifunctional reactive diluent, and a tetrafunctional reactive diluent, wherein: The monofunctional reactive diluent includes ethyl acrylate, butyl acrylate, methyl acrylate and / or methyl methacrylate; The bifunctional reactive diluent includes dipropylene glycol diacrylate, tripropylene glycol diacrylate and / or epoxy resin diacrylate; The trifunctional reactive diluent includes trimethylolpropane triethylene ester.

21. The preparation method according to claim 9, wherein The salt-forming agent used in the neutralization and salt formation is triethylamine.

22. The preparation method according to claim 9, wherein The temperature of the neutralization salt formation is 30-50° C., and the time is 10-30 min.

23. The preparation method according to claim 9, wherein The emulsification time for adding water is 10~30 min.

24. Use of the emulsion according to any one of claims 1 to 8 or the emulsion prepared according to the method of claim 9 or 23 as a photosensitive dry film precursor, the use comprising: A photoinitiator is added to the emulsion, and then coating and drying are performed to obtain a photosensitive dry film.

25. The use according to claim 24, wherein The photoinitiator is 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone and / or 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone.

26. The use according to claim 24, wherein: The coating thickness is 20-100 μm, and the drying temperature is 40-70° C.

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