CN112063209A - Photo-polymerization method for synthesizing photo-curing acrylate PCB protective coating - Google Patents
Photo-polymerization method for synthesizing photo-curing acrylate PCB protective coating Download PDFInfo
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- CN112063209A CN112063209A CN202010895669.7A CN202010895669A CN112063209A CN 112063209 A CN112063209 A CN 112063209A CN 202010895669 A CN202010895669 A CN 202010895669A CN 112063209 A CN112063209 A CN 112063209A
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- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000006116 polymerization reaction Methods 0.000 title claims abstract description 24
- 239000011253 protective coating Substances 0.000 title claims abstract description 17
- 238000000016 photochemical curing Methods 0.000 title claims abstract description 16
- 230000002194 synthesizing effect Effects 0.000 title claims abstract description 6
- 239000000178 monomer Substances 0.000 claims abstract description 57
- 239000011248 coating agent Substances 0.000 claims abstract description 53
- 238000000576 coating method Methods 0.000 claims abstract description 53
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims abstract description 26
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims abstract description 26
- PSGCQDPCAWOCSH-UHFFFAOYSA-N (4,7,7-trimethyl-3-bicyclo[2.2.1]heptanyl) prop-2-enoate Chemical compound C1CC2(C)C(OC(=O)C=C)CC1C2(C)C PSGCQDPCAWOCSH-UHFFFAOYSA-N 0.000 claims abstract description 23
- 238000006243 chemical reaction Methods 0.000 claims abstract description 21
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 claims abstract description 18
- 150000001412 amines Chemical class 0.000 claims abstract description 16
- 239000003999 initiator Substances 0.000 claims abstract description 16
- 238000004132 cross linking Methods 0.000 claims abstract description 10
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 9
- 238000002360 preparation method Methods 0.000 claims abstract description 6
- FIHBHSQYSYVZQE-UHFFFAOYSA-N 6-prop-2-enoyloxyhexyl prop-2-enoate Chemical compound C=CC(=O)OCCCCCCOC(=O)C=C FIHBHSQYSYVZQE-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000002994 raw material Substances 0.000 claims abstract description 4
- 239000002131 composite material Substances 0.000 claims description 18
- 238000002156 mixing Methods 0.000 claims description 7
- QNODIIQQMGDSEF-UHFFFAOYSA-N (1-hydroxycyclohexyl)-phenylmethanone Chemical compound C=1C=CC=CC=1C(=O)C1(O)CCCCC1 QNODIIQQMGDSEF-UHFFFAOYSA-N 0.000 claims description 6
- 238000005286 illumination Methods 0.000 claims description 4
- 238000005303 weighing Methods 0.000 claims description 2
- 239000002519 antifouling agent Substances 0.000 claims 2
- ZDHCZVWCTKTBRY-UHFFFAOYSA-N omega-Hydroxydodecanoic acid Natural products OCCCCCCCCCCCC(O)=O ZDHCZVWCTKTBRY-UHFFFAOYSA-N 0.000 claims 1
- 238000001723 curing Methods 0.000 abstract description 20
- 238000012662 bulk polymerization Methods 0.000 abstract description 5
- 230000035484 reaction time Effects 0.000 abstract description 4
- 238000004134 energy conservation Methods 0.000 abstract description 2
- 230000000977 initiatory effect Effects 0.000 abstract description 2
- 239000003607 modifier Substances 0.000 abstract description 2
- 239000007787 solid Substances 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 14
- 238000010521 absorption reaction Methods 0.000 description 9
- 150000003839 salts Chemical class 0.000 description 9
- 239000000853 adhesive Substances 0.000 description 6
- 230000001070 adhesive effect Effects 0.000 description 6
- 239000003973 paint Substances 0.000 description 6
- 239000007921 spray Substances 0.000 description 6
- 229920001577 copolymer Polymers 0.000 description 5
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 230000004580 weight loss Effects 0.000 description 5
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000007334 copolymerization reaction Methods 0.000 description 3
- 238000002329 infrared spectrum Methods 0.000 description 3
- 229920002521 macromolecule Polymers 0.000 description 3
- 150000003254 radicals Chemical class 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229920001688 coating polymer Polymers 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- -1 peroxy radicals Chemical class 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000010526 radical polymerization reaction Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000002966 varnish Substances 0.000 description 2
- DKPFZGUDAPQIHT-UHFFFAOYSA-N Butyl acetate Natural products CCCCOC(C)=O DKPFZGUDAPQIHT-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 1
- 238000004566 IR spectroscopy Methods 0.000 description 1
- CERQOIWHTDAKMF-UHFFFAOYSA-M Methacrylate Chemical compound CC(=C)C([O-])=O CERQOIWHTDAKMF-UHFFFAOYSA-M 0.000 description 1
- 229920001730 Moisture cure polyurethane Polymers 0.000 description 1
- 150000001252 acrylic acid derivatives Chemical class 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 150000001602 bicycloalkyls Chemical group 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 229920006037 cross link polymer Polymers 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- FUZZWVXGSFPDMH-UHFFFAOYSA-N hexanoic acid Chemical compound CCCCCC(O)=O FUZZWVXGSFPDMH-UHFFFAOYSA-N 0.000 description 1
- TUJKJAMUKRIRHC-UHFFFAOYSA-N hydroxyl Chemical compound [OH] TUJKJAMUKRIRHC-UHFFFAOYSA-N 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000012844 infrared spectroscopy analysis Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 150000003071 polychlorinated biphenyls Chemical class 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 238000011417 postcuring Methods 0.000 description 1
- 150000003141 primary amines Chemical class 0.000 description 1
- 238000003847 radiation curing Methods 0.000 description 1
- 150000003335 secondary amines Chemical class 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000002411 thermogravimetry Methods 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D4/00—Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16
- C09D4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09D159/00 - C09D187/00
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/46—Polymerisation initiated by wave energy or particle radiation
- C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/10—Esters
- C08F220/12—Esters of monohydric alcohols or phenols
- C08F220/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
- C08F220/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
- C08F220/1811—C10or C11-(Meth)acrylate, e.g. isodecyl (meth)acrylate, isobornyl (meth)acrylate or 2-naphthyl (meth)acrylate
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
- Paints Or Removers (AREA)
Abstract
The invention provides a photo-polymerization method for synthesizing a photo-curing acrylate PCB protective coating, which comprises the following raw materials: an acrylate prepolymer; 18-20% of the total mass of the acrylate prepolymer of crosslinking monomer 1, 6-hexanediol diacrylate; initiator auxiliary agent active amine with 0-2% of total mass of acrylate prepolymer; initiator auxiliary agent with 0-3% of total mass of acrylate prepolymer; the acrylate prepolymer is prepared from the following components in a mass ratio of 4: 6-5: 0-1 Butyl Acrylate (BA) monomer, isobornyl acrylate (IBOA) monomer and Acrylic Acid (AA) monomer. According to the invention, ultraviolet light is used for initiating acrylate bulk polymerization reaction to a certain degree to obtain an acrylate prepolymer, and then a modifier is added into the prepolymer to adjust various properties of the prepolymer after curing. The acrylate prepolymer synthesized by the photopolymerization method has the characteristics of short reaction time (several minutes or even tens of seconds), small influence of temperature on reaction, energy conservation, no VOC, hundred percent of solid content and the like, can adjust the viscosity of the coating by controlling the polymerization reaction degree of a light source according to the coating and process requirements in the preparation process, and is simple to use and good in adjustability.
Description
Technical Field
The invention relates to the technical field of PCB (printed circuit board) protective coatings, in particular to a photocuring acrylate PCB protective coating synthesized by a photopolymerization method.
Background
PCB is an important component in electrical products, relays, navigation instruments, precision instruments, electronic components and the like [1-2 ]. Under severe environment, such as operation at sea, aviation, mine, short circuit between the solder points on the surface of PCB is easily caused to cause the fault of the circuit system because of the influence of moisture, humidity, dust and other conditions in the air [3 ]. The most effective solution to this problem is to coat a layer of protective coating on the surface of the PCB to help the PCB resist the effects of the harsh environment on it, thereby increasing its service life. The acrylate PCB protective coating has the performances of high transparency, high adhesive force, heat resistance, chemical corrosion resistance, aging resistance and the like [4-6 ]. However, the acrylate protective coatings currently used for PCBs are either solvent-based or water-based. The solvent-based coating has volatile solvent, and pollutes the environment; if the water-based paint is used, the PCB is more easily damaged due to the existence of moisture. .
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for synthesizing a photocuring acrylate PCB protective coating by a photopolymerization method, and solves the technical problems that the conventional acrylate PCB protective coating has volatile solvents, pollutes the environment or is easy to damage the PCB due to moisture.
The technical scheme of the invention is as follows: the photo-polymerization method is used for synthesizing the photo-curing acrylate PCB protective coating, and the raw materials comprise: an acrylate prepolymer; 18-20% of the total mass of the acrylate prepolymer of crosslinking monomer 1, 6-hexanediol diacrylate; initiator auxiliary agent active amine with 0-2% of total mass of acrylate prepolymer; initiator auxiliary agent with 0-3% of total mass of acrylate prepolymer;
the acrylate prepolymer is prepared from the following components in a mass ratio of 4: 6-5: 0-1 Butyl Acrylate (BA) monomer, isobornyl acrylate (IBOA) monomer and Acrylic Acid (AA) monomer.
The initiator auxiliary agent is prepared from the following components in a mass ratio of 1:1:1 photoinitiator 1173, photoinitiator 184 and photoinitiator TPO.
The preparation method of the photo-polymerization synthesized photo-curing acrylate PCB protective coating comprises the following steps:
(5) weighing the components according to the formula;
(6) mixing isobornyl acrylate (IBOA) monomer, Butyl Acrylate (BA) monomer and Acrylic Acid (AA) monomer, adding photoinitiator 1173, and uniformly mixing to obtain a mixed monomer;
(7) adding a mixed monomer into a dry clean tubular reactor, selecting a UV LED (lambda 365nm) light source to irradiate from the side surface of the dry clean tubular reactor to initiate monomer polymerization for 60s, and then stopping illumination to obtain an acrylate prepolymer;
(8) and adding a crosslinking monomer HDDA, a composite photoinitiator and active amine into the acrylate prepolymer, and uniformly mixing to obtain the photocuring coating.
The composite photoinitiator consists of a photoinitiator 1173, a photoinitiator 184 and a photoinitiator TPO in a mass ratio of 1:1: 1.
In the acrylate prepolymer, the conversion rates of C ═ C double bonds are 58.43% to 60.45%, respectively.
According to the invention, ultraviolet light is used for initiating acrylate bulk polymerization reaction to a certain degree to obtain an acrylate prepolymer, and then a modifier is added into the prepolymer to adjust various properties of the prepolymer after curing. The acrylate prepolymer synthesized by the photopolymerization method has the characteristics of short reaction time (several minutes or even tens of seconds), small influence of temperature on reaction, energy conservation, no VOC, hundred percent of solid content and the like, can adjust the viscosity of the coating by controlling the polymerization reaction degree of a light source according to the coating and process requirements in the preparation process, and is simple to use and good in adjustability.
Drawings
FIG. 1 is a schematic diagram of a tubular reactor used in the experiment.
FIG. 2 Co-polymerization conversion rates of BA and IBOA.
FIG. 3 Effect of composite initiator on photocuring rate.
FIG. 4 influence of composite initiator on film hardness.
FIG. 5 is an infrared spectrum before and after curing.
FIG. 6 TG and DTG curves of the coating films.
Detailed Description
In order to make the object, technical solution and technical effect of the present invention more apparent, the present invention will be further described with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Preparation of photocuring acrylate PCB protective coating
1. Raw materials: butyl Acrylate (BA), Acrylic Acid (AA): pure analysis, chemical reagent factory of Fochen, Tianjin; isobornyl acrylate (IBOA): tianjiao radiation curing materials, Inc., Tianjin; 1, 6-hexanediol diacrylate (HDDA), type 8211, active amine, type 1113D: analytically pure, kontian electronics materials ltd, zhongshan city; photoinitiator 1173, photoinitiator 184: analytical grade, basf applied chemical limited; photoinitiator TPO: analytically pure, Tianjin Jiu chemical Co.
2. Preparation method
Isobornyl acrylate (IBOA) monomer, Butyl Acrylate (BA) monomer and Acrylic Acid (AA) monomer are weighed and mixed, then photoinitiator 1173 is added, and the mixture is uniformly mixed to obtain the mixed monomer. As shown in fig. 1, a stirrer 3 and a thermometer are arranged in a dry clean tubular reactor 1, a prepared mixed monomer containing a photoinitiator 1173 is added into the reactor, a UV LED (λ 365nm) light source 2 is selected to irradiate from the side surface of the dry clean tubular reactor 1 to initiate monomer polymerization to a certain reaction degree, and then illumination is stopped to obtain an acrylate prepolymer; and adding a crosslinking monomer HDDA, a composite photoinitiator and active amine into the acrylate prepolymer, and uniformly mixing to obtain the photocuring coating. The composite photoinitiator consists of a photoinitiator 1173, a photoinitiator 184 and a photoinitiator TPO in a mass ratio of 1:1: 1.
Secondly, the performance of the synthesized photocureable coating is tested, and the test method is as follows
The photocurable coating was coated on the PCB board with a film coater having a film thickness of 100 μm and irradiated with a high-pressure mercury lamp having a power of 1000W for 40S, and the performance thereof was tested according to the following criteria. The adhesion is determined by reference to GB/T9286-1998 test for marking test of paint films of colored paint and varnish; the coating hardness is determined according to GB/T6739 and 1996 pencil determination method for coating hardness; soaking for 168h according to GB/T1733-93 'determination method for water resistance of paint film', and observing whether the paint film has phenomena of light loss, falling off, softening, foaming, etc.; salt fog resistance reference GB/T1771-2007Determination of neutral salt spray resistance of colored paints and varnishes "; thermal behavior is measured by using a synchronous thermal analyzer at O2Testing under the atmosphere, wherein the temperature range is 0-800 ℃, and the heating rate is 10 ℃/min; and performing structural characterization on the coating film by using Fourier infrared spectroscopy (FT-IR).
Three results and discussion
1. Determination of prepolymerization time
The photopolymerization reaction rate is very high, and when bulk polymerization is adopted, the polymerization time is short, the reaction degree is too low, and the low viscosity and the long post-curing time of the prepolymer are directly caused; the polymerization time is long, the viscosity of the system is high, the sudden polymerization is easy to occur, and the reaction degree is greatly changed within a few seconds, so that the control of the prepolymerization time is very important. Therefore, it is impossible to find a suitable prepolymerization time by completely reacting the monomers by bulk polymerization. The applicant determined suitable bulk prepolymerization times by studying the solution polymerization process of BA and IBOA. FIG. 2 is a plot of the copolymerization conversion rate determined by iodometric titration, where photoinitiator 1173 is 0.83% o and the monomer to butyl acetate solvent ratio is 1: 1.
In FIG. 2, 1, 2 and 3 are the initial stage, the middle stage and the later stage of polymerization, respectively, in which the induction period of photopolymerization is very short and is inconvenient to make. The reaction time is taken as the optimum prepolymerization time by drawing tangents to the intersection points of adjacent polymerization periods and making the tangents meet at one point.
The concentration of the initiator used in the prepolymerization is 0.42 per thousand, the concentration of the monomer is 2 times of that of the solution polymerization, the concentration of the initiator used in the solution polymerization is 0.83 per thousand, and the initiator is obtained by the formula (1) on the assumption that the rate constant is equal to the efficiency of the initiator
Rp∝[I]1/2·[M] (1)
Rp(solution polymerization)And Rp(bulk polymerization)The ratio was 0.71. assuming that the optimum reaction time for bulk prepolymerization was t and the monomer conversion after reaction ts was the same as the monomer conversion for solution polymerization 84 s.
Then t is 0.71 x 84.02 x 59.65s
Thus, the prepolymerization time was experimentally set to 60s, at which time the monomer copolymerization conversion was around 61%.
2. Effect of functional monomer AA on coating film Performance
The methacrylate monomers have low photopolymerization activity, so BA, IBOA and modified monomer AA in the acrylate monomers are selected as prepolymer monomers. The huge nonpolar bicycloalkyl in the molecular structure of the IBOA gives great steric hindrance protection to a polymer molecular chain, the intermolecular force is reduced, so that the adhesive force is good, and the polar group in the AA can improve the film coating performance. 3 percent of composite photoinitiator is added into the prepared prepolymer, and the coating is cured. Table 1 shows the effect of the mass ratio of different AA and IBOA in the prepolymer on the coating properties.
TABLE 1 AA Effect on coating film Performance
More X means poorer water resistance
Strong polar carboxyl in AA can form intermolecular force with the surface of the PCB to improve the adhesive force of the coating; and meanwhile, the carboxyl is a strong water-absorbing group, so that the water resistance and the salt spray resistance of the material are reduced. With the increase of AA, a large amount of hydrogen bonds are formed between polymer molecular chains due to excessive carboxyl groups, so that the hardness is improved, and the adhesion of the coating to a PCB is finally reduced.
3. Effect of crosslinking monomer HDDA on coating Properties
The water resistance and the salt spray resistance of the material are reduced due to the addition of AA. The cross-linked HDDA monomer is selected for the experiment to improve the water resistance and the salt spray resistance of the coating. The mass ratio of the fixed prepolymer monomer is 6(BA):4(IBOA):1(AA), HDDA and 3% composite photoinitiator in different proportions are added into the prepolymer, and the coating is cured, and the properties are shown in Table 2.
TABLE 2 influence of HDDA on coating film Properties
More x means poorer water resistance; means that the coating film is soft after curing and that the hardness and adhesion measured are of no practical significance
With the increase of HDDA, the unreacted monomer in the coating curing system reacts with HDDA to generate an interpenetrating network structure through crosslinking, so that micromolecular water is prevented from entering macromolecules to a greater extent, the rigidity of the coating polymer is increased, the water resistance, the salt spray resistance and the hardness of the coating polymer are improved, and the adhesive force is finally reduced.
4. Effect of photoinitiators on curing of coating films
The amount of photoinitiator directly affects the cure rate of the coating. The photoinitiator 1173, 184 and TPO have different maximum absorption wavelength ranges and different decomposition rates under the irradiation of ultraviolet light. The composite photoinitiator is selected in the experiment, the absorption wavelength range of the composite photoinitiator is expanded, and the coating is rapidly cured. A prepolymer monomer mass ratio of 6(BA):4(IBOA):1(AA) is selected, 18 percent of HDDA and different amounts of composite photoinitiator are added into the prepolymer, and a coating film is cured, wherein the curing rate and the hardness of the coating film are shown in figures 3 and 4.
As can be seen from FIGS. 3 and 4, as the composite photoinitiator increases, the free radicals generated in the same illumination time increase, the curing rate of the coating film is increased, and the crosslinking density is increased, so that the hardness of the coating film after curing is improved. Because some harmful byproducts are generated after the photoinitiator is decomposed inevitably, TPO can deepen the yellow color of a coating film and comprehensively considers that the light transmission is poor, and the using amount of the composite initiator which is selected during the curing of the coating film is 3 percent.
5. Effect of active amine addition on coating film Performance
The mass ratio of the pre-polymerized monomers is 6(BA):4(IBOA):1(AA), 3% of composite photoinitiator, 18% of HDDA and different proportions of active amine are added into the pre-polymer, and the coating is cured, wherein the curing time and the performance of the coating are shown in Table 3.
TABLE 3 Effect of active amine amount on coating film Performance
More X indicates poorer water resistance, and the difference in surface dryness indicates that one layer of the surface is less hard or tacky
During the light curing process, the surface of the coating is directly contacted with airWhen the surface is contacted with the epoxy resin, free radicals generated on the surface can easily react with oxygen in the air to generate low-activity peroxy radicals, so that the surface is not cured completely. However, the peroxy radical can abstract active hydrogen in the active amine to generate hydroperoxide, and high-activity alkoxy radical and hydroxyl radical are generated under the irradiation of ultraviolet light to continue to initiate polymerization so as to enable the coating to be cured more thoroughly[11]. The addition of the active amine can improve the curing time, the surface drying performance, the salt fog resistance and the hardness of the coating without reducing the adhesive force, but the water resistance and the salt fog resistance of the coating are finally reduced due to the poor water resistance of the active amine.
6. Infrared spectroscopic analysis
In the photopolymerization reaction, the free radical decomposed by the photoinitiator can initiate the polymerization reaction of the C ═ C double bond in the unsaturated acrylate monomer. The absorption peak of C ═ C in the infrared spectrum reflects the degree of reaction of the monomers. FIG. 5 is an infrared spectrum of acrylate polymerization time 0s (mixed monomer), polymerization 60s (prepolymer), and post-cure 35s (coating).
As can be seen from FIG. 5, after polymerization for 60s, the C ═ C double bond was found to be 1628cm-1The sum of the absorption peaks at position (C-H) is 809cm-1The absorption peak is greatly reduced[12,13]The content of C ═ C double bonds is shown to be greatly reduced; the absorption peaks at the two positions of the coating after curing basically disappear, which indicates that the C ═ C double bond is basically completely reacted after curing. After curing at 2956cm-1And 2876cm-1The saturated C-H absorption peak is reduced, and a micro-crosslinked copolymer is probably obtained by transferring to a macromolecule alpha-H chain in the free radical polymerization process; in the curing process, because the active amine is added into the photocureable coating, the coating contains carboxyl, and after curing, the coating is 3449cm in an infrared spectrogram-1The absorption peaks of primary and secondary amines or amides appear.
By respectively comparing 1618cm in 1 and 2 spectrograms-1And 809cm-1The peak areas obtained by integrating the two absorption peaks gave respective conversions of C ═ C double bonds of 60.45% and 58.43%, which were comparable to the expected conversions.
7. Thermogravimetric analysis of photocurable PCB protective coatings
The applicant studied the thermal stability of the coating prepared under the process conditions of optimum effect after curing of the coating film, and the TG and DTG curves thereof are shown in fig. 6.
As can be seen from FIG. 6, the thermal decomposition of the cured coating film is mainly carried out in four stages of 235-370 deg.C, 370-430 deg.C, and 430-610 deg.C, and the total weight loss process is carried out in 235-610 deg.C, which results in good thermal stability. The first stage is mainly weight loss caused by the breaking and burning of the molecular chain of the acrylate copolymer which is not crosslinked in the prepolymer; the second stage is a weight loss process of the cross-linked copolymer to a certain extent obtained by transferring to a macromolecule alpha-H chain in the free radical polymerization process, and the stability of the weight loss process is greater than that of the non-cross-linked polymer; the third stage is the weight loss process of the crosslinked copolymer obtained by copolymerizing the HDDA and the residual mixed monomers in the curing process, the rigidity of the crosslinked copolymer is further increased, and the thermal stability is very good.
4 conclusion
In the experiment, an ultraviolet polymerization method is adopted to synthesize an acrylate prepolymer, and the acrylate prepolymer is taken as a main body, and a crosslinking monomer HDDA, an initiator auxiliary agent active amine and a composite photoinitiator are added to prepare the photocureable coating. When the mass ratio of the monomers in the acrylate prepolymer is 6(BA):4(IBOA):1(AA) and the prepolymer is prepolymerized for 60s, the monomer conversion rate is about 60 percent; when the amount of the HDDA is 18% of the prepolymer, the amount of the composite photoinitiator is 3% of the prepolymer, and the amount of the active amine is 2% of the prepolymer, the coating is cured for 35s, the hardness is 2H, the adhesive force is grade 1, the water-resistant time is more than 168H, the salt spray resistant time is more than 110H, and the comprehensive performance is optimal.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the present invention pertains, the architecture form can be flexible and varied without departing from the concept of the present invention, and a series of products can be derived. But rather a number of simple derivations or substitutions are made which are to be considered as falling within the scope of the invention as defined by the appended claims.
Claims (5)
1. The photo-polymerization method for synthesizing the photo-curing acrylate PCB protective coating is characterized in that the photo-polymerization method comprises the following raw materials: an acrylate prepolymer; 18-20% of the total mass of the acrylate prepolymer of crosslinking monomer 1, 6-hexanediol diacrylate; initiator auxiliary agent active amine with 0-2% of total mass of acrylate prepolymer; initiator auxiliary agent with 0-3% of total mass of acrylate prepolymer;
the acrylate prepolymer is prepared from the following components in a mass ratio of 4: 6-5: 0-1 Butyl Acrylate (BA) monomer, isobornyl acrylate (IBOA) monomer and Acrylic Acid (AA) monomer.
2. The photopolymerization-process synthesized photocuring acrylate PCB protective paint according to claim 1, wherein the initiator auxiliary agent is prepared from the following components in a mass ratio of 1:1:1 photoinitiator 1173, photoinitiator 184 and photoinitiator TPO.
3. The method for preparing a photo-polymerization synthesized photo-curing acrylate PCB protective coating according to claim 1 or 2, which is characterized by comprising the following steps:
(1) weighing the components according to the formula;
(2) mixing isobornyl acrylate (IBOA) monomer, Butyl Acrylate (BA) monomer and Acrylic Acid (AA) monomer, adding photoinitiator 1173, and uniformly mixing to obtain a mixed monomer;
(3) adding a mixed monomer into a dry clean tubular reactor, selecting a UV LED (lambda 365nm) light source to irradiate from the side surface of the dry clean tubular reactor to initiate monomer polymerization for 60s, and then stopping illumination to obtain an acrylate prepolymer;
(4) and adding a crosslinking monomer HDDA, a composite photoinitiator and active amine into the acrylate prepolymer, and uniformly mixing to obtain the photocuring coating.
4. The preparation method of the photocuring acrylate PCB protective paint synthesized by the photopolymerization method as claimed in claim 1 or 2, wherein the composite photoinitiator consists of a photoinitiator 1173, a photoinitiator 184 and a photoinitiator TPO in a mass ratio of 1:1: 1.
5. The method for preparing a photo-curable acrylate PCB protective coating synthesized by a photopolymerization method according to claim 1 or 2, wherein the conversion rates of C ═ C double bonds in the acrylate prepolymer are 58.43% to 60.45%, respectively.
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| EP0822448A1 (en) * | 1996-08-02 | 1998-02-04 | E.I. Du Pont De Nemours And Company | Flexible, flame-retardant, photoimageable composition for coating printed circuits |
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| CN108329439A (en) * | 2018-03-20 | 2018-07-27 | 成都晨光博达橡塑有限公司 | A kind of methacrylic resin composition |
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| EP0822448A1 (en) * | 1996-08-02 | 1998-02-04 | E.I. Du Pont De Nemours And Company | Flexible, flame-retardant, photoimageable composition for coating printed circuits |
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