Low shrinkage resin and preparation method thereof

Abstract

The present invention discloses a low-shrinkage resin and a preparation method thereof, belonging to the technical field of resin materials. The present invention comprises synthesizing a maleic anhydride-p-phenylenediamine derivative from maleic anhydride and p-phenylenediamine; preliminarily polymerizing VAc under the action of a composite initiator to obtain a PVAc preliminary polymer; preparing a PVAc graft by combining the maleic anhydride-p-phenylenediamine derivative and the PVAc preliminary polymer under the action of an initiator; and irradiating a base resin, a photoinitiator, and an additive under ultraviolet light to obtain the low-shrinkage resin. The low-shrinkage resin prepared by the present invention has a high gel fraction of more than 75%; a low shrinkage rate, characterized by a linear shrinkage rate of less than 1.25%, and good thermal stability.

Description

Technical Field

[0001] The invention belongs to the technical field of resin materials, and particularly relates to a low-shrinkage resin and a preparation method thereof. Background Art

[0002] Unsaturated polyester resin (UPR) and its composites are widely used due to their excellent mechanical properties and processability. However, during the curing process, cross-linking and intense heat release generate internal stress, leading to internal microcracks, reducing the bending strength of the product, and causing a volume shrinkage of 7%-10%. This results in low dimensional accuracy, surface ripples, and depressions, hindering the application of UPR and its composites.

[0003] Currently, a common method for reducing the shrinkage of unsaturated polyester resins is to add a macromolecular weight low-shrinkage agent to the resin. This agent expands upon heating and separates from the resin, creating micropores that compensate for curing shrinkage. Macromolecular weight low-shrinkage agents are categorized by polarity: polar, neutral, and non-polar. Typical examples include PVAc, polymethyl methacrylate (PMMA), and polystyrene (PS). Among these, the polar low-shrinkage agent polyvinyl acetate (PVAc) exhibits excellent compatibility with the resin, offers the best anti-shrinkage effect, and is the most widely used. However, PVAc can significantly reduce the strength of finished products. Summary of the Invention

[0004] The object of the present invention is to provide a PVAc grafted product which can be used to reduce the shrinkage rate of resin, can be used in adhesives, has good emulsification, good dilution stability and good compression shear performance after bonding.

[0005] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0006] A PVAc graft comprising:

[0007] PVAc segment; and a graft segment bonded thereto;

[0008] The content of the graft segment is less than 26.47 wt%.

[0009] Preferably, the content of the graft segments is not 0 wt%.

[0010] Preferably, the grafted material is a maleic anhydride-p-phenylenediamine derivative. By introducing the maleic anhydride-p-phenylenediamine derivative into PVAc as the grafted material segment, a rigid structure is provided, the content of polar groups is increased, and a higher affinity is provided, thereby improving the performance of PVAc, thereby increasing the applicability of PVAc and expanding the uses of the PVAc grafted material. The PVAc grafted material obtained by this method has good emulsification properties, good compression and shear properties after adhesive bonding, good dilution stability after emulsification to form an emulsion, and improved bonding strength after adhesive bonding.

[0011] Preferably, a cross-linked structure exists in the PVAc graft. The amine nitrogen in the maleic anhydride-p-phenylenediamine derivative reacts with two molecules of maleic anhydride to form a three-molecule bonded structure. The maleic anhydride-p-phenylenediamine derivative contains two sets of double bonds, which can repeatedly bond with the PVAc segment to form a cross-linked structure.

[0012] Preferably, the number average molecular weight of the PVAc segment in the PVAc graft is greater than 2500 g / mol.

[0013] Preferably, the number average molecular weight of the PVAc segment in the PVAc graft is less than 6000 g / mol.

[0014] Preferably, the molecular weight distribution (Mw / Mn) value of the PVAc segment in the PVAc graft falls above 1.2.

[0015] Preferably, the molecular weight distribution (Mw / Mn) value of the PVAc segment in the PVAc graft falls below 1.8.

[0016] The invention discloses application of PVAc grafts in low-shrinkage resins.

[0017] The object of the present invention is to provide a low-shrinkage resin with high gel fraction, low shrinkage and good thermal stability.

[0018] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0019] A low-shrinkage resin includes the aforementioned PVAc graft. During the curing process of unsaturated resin, internal stress is generated, leading to internal microcracks. After the PVAc graft is evenly distributed in the resin, it partially offsets the stress during the curing process of the unsaturated resin, compensates for the internal cracks, reduces the shrinkage of the resin, and prevents problems such as cracks and resin surface irregularities caused by curing shrinkage.

[0020] Preferably, the content of the PVAc graft is 5.93% or more.

[0021] Preferably, the content of the PVAc graft is less than 29.36%.

[0022] Preferably, the low shrinkage resin contains a photoinitiator.

[0023] More preferably, the photoinitiator is a triarylsulfonium hexafluoroantimonate.

[0024] More preferably, the content of the photoinitiator is 0.74 wt % or more.

[0025] More preferably, the content of the photoinitiator is 2.75 wt % or less.

[0026] Preferably, the PVAc grafts are dispersed in a cross-linked matrix resin.

[0027] More preferably, the matrix resin is an epoxy resin.

[0028] Preferably, the thickness of the low shrinkage resin does not exceed 30 mm.

[0029] Preferably, the linear shrinkage of the low shrinkage resin is 1.25% or less.

[0030] The object of the present invention is to provide a method for preparing a low-shrinkage resin with high gel fraction, low shrinkage and good thermal stability.

[0031] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0032] A method for preparing a low-shrinkage resin, comprising:

[0033] Maleic anhydride-p-phenylenediamine derivatives can be synthesized from maleic anhydride and p-phenylenediamine;

[0034] VAc is preliminarily polymerized under the action of a composite initiator to obtain a PVAc preliminarily polymer;

[0035] The PVAc grafted product is prepared by reacting a maleic anhydride-p-phenylenediamine derivative with a PVAc preliminary polymer under the action of an initiator;

[0036] The low shrinkage resin is prepared by combining a base resin, a photoinitiator and an additive under ultraviolet light conditions.

[0037] Preferably, the composite initiator is azobisisobutyronitrile and 1,1'-azo(cyanocyclohexane).

[0038] Preferably, in the preparation of maleic anhydride-p-phenylenediamine derivatives, maleic anhydride and p-phenylenediamine are added to a solvent, reacted at a temperature of 20-40°C for 3-12 hours under nitrogen protection, heated to a temperature of 50-70°C for 3-12 hours, cooled to room temperature, ether is added for precipitation, filtered, washed with deionized water, and vacuum dried to obtain the maleic anhydride-p-phenylenediamine derivative.

[0039] More preferably, the solvent is DMF.

[0040] More preferably, the amount of maleic anhydride added is 21-86 wt % of the solvent.

[0041] More preferably, the added amount of p-phenylenediamine is 10-40 wt % of the solvent.

[0042] More preferably, the amount of maleic anhydride added is 1.82 times or more of the amount of p-phenylenediamine added.

[0043] More preferably, the amount of diethyl ether added is 100 wt % or more of the solvent.

[0044] Preferably, VAc preliminary polymerization: VAc and composite initiator are mixed, stirred and reacted at 80-100°C for 20-60 minutes under inert gas protection, THF is added to dissolve after cooling, and then n-hexane is added to precipitate, and the mixture is allowed to stand for 1-3 hours, and filtered to obtain a preliminary PVAc polymer.

[0045] More preferably, the composite initiator is a mixture of azobisisobutyronitrile and 1,1'-azo(cyanocyclohexane) in a mass ratio of 1:0.1-0.2.

[0046] More preferably, the added amount of the composite initiator is 0.2-0.5 wt % of the amount of VAc used.

[0047] More preferably, the amount of THF added is 150-300 wt% of the amount of VAc used.

[0048] More preferably, the amount of n-hexane added is 200-500 wt % of THF.

[0049] Preferably, the preparation of the PVAc grafted compound: the PVAc preliminary polymer, maleic anhydride-p-phenylenediamine derivative, and the initiator are mixed, and under the protection of an inert gas, the mixture is stirred and reacted at a temperature of 80-100°C for 0.5-3h. After cooling, THF is added to dissolve the mixture, and then n-hexane is added to precipitate the mixture. The mixture is allowed to stand for 1-3h, and the PVAc grafted compound is obtained by filtration.

[0050] More preferably, the initiator is azobisisobutyronitrile.

[0051] More preferably, the addition amount of the maleic anhydride-p-phenylenediamine derivative is 12-36 wt % of the PVAc preliminary polymer.

[0052] More preferably, the added amount of the initiator is 0.1-0.6 wt % of the PVAc preliminary polymer.

[0053] More preferably, the amount of THF added is 150-300 wt % of the amount of PVAc preliminary polymer used.

[0054] More preferably, the amount of n-hexane added is 200-500 wt % of THF.

[0055] Preferably, the low shrinkage resin is prepared by uniformly mixing the base resin, the photoinitiator and the additives, defoaming the mixture, and curing the mixture under ultraviolet light for 5-10 minutes to obtain the low shrinkage resin.

[0056] More preferably, the matrix resin is an epoxy resin.

[0057] More preferably, the photoinitiator is a triarylsulfonium hexafluoroantimonate.

[0058] More preferably, the amount of the photoinitiator added is 1-3 wt % of the base resin.

[0059] More preferably, the additive is a PVAc graft, and the amount of the additive added is 8-32 wt % of the base resin.

[0060] The present invention utilizes a PVAc grafted with a maleic anhydride-p-phenylenediamine derivative as an additive to prepare a low-shrinkage resin. The low-shrinkage resin exhibits the following beneficial effects: a high gel fraction of 75% or greater; a low shrinkage rate, characterized by a linear shrinkage rate of 1.25% or less; and excellent thermal stability. Therefore, the present invention provides a method for preparing a low-shrinkage resin having a high gel fraction, a low shrinkage rate, and excellent thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is the infrared image of PVAc graft;

[0062] Figure 2 This is the gel ratio diagram of low shrinkage resin;

[0063] Figure 3 This is the linear shrinkage diagram of low shrinkage resin. DETAILED DESCRIPTION

[0064] The technical solution of the present invention is further described in detail below with reference to the specific embodiments and the accompanying drawings:

[0065] Example 1:

[0066] Preparation of maleic anhydride-p-phenylenediamine derivatives: maleic anhydride and p-phenylenediamine are added to a solvent, reacted at 30°C for 3 hours under nitrogen protection, heated to 60°C for 6 hours, cooled to room temperature, added with diethyl ether for precipitation, filtered, washed with deionized water, and vacuum dried to obtain maleic anhydride-p-phenylenediamine derivatives; the solvent is DMF, the amount of maleic anhydride added is 40wt% of the solvent, the amount of p-phenylenediamine added is 20wt% of the solvent, and the amount of diethyl ether added is 300wt% of the solvent.

[0067] VAc preliminary polymerization: VAc and composite initiator were mixed, stirred and reacted at 90°C for 30 minutes under inert gas protection, THF was added to dissolve after cooling, and then n-hexane was added to precipitate. The mixture was allowed to stand for 3 hours and filtered to obtain a PVAc preliminary polymer. The composite initiator was a mixture of azobisisobutyronitrile and 1,1'-azo(cyanocyclohexane) in a mass ratio of 1:0.12. The amount of composite initiator added was 0.35wt% of the amount of VAc used, the amount of THF added was 200wt% of the amount of VAc used, and the amount of n-hexane added was 300wt% of THF.

[0068] Preparation of PVAc grafted polymer: A PVAc preliminary polymer, a maleic anhydride-p-phenylenediamine derivative, and an initiator were mixed and stirred at 90°C under inert gas for 1.5 hours. After cooling, THF was added to dissolve the mixture, followed by precipitation with n-hexane. The mixture was allowed to stand for 3 hours and filtered to obtain the PVAc grafted polymer. The initiator was azobisisobutyronitrile. The amount of maleic anhydride-p-phenylenediamine derivative added was 17 wt% of the PVAc preliminary polymer, the amount of initiator added was 0.5 wt% of the PVAc preliminary polymer, the amount of THF added was 200 wt% of the PVAc preliminary polymer used, and the amount of n-hexane added was 300 wt% of the THF.

[0069] Preparation of low-shrinkage resin: The base resin, photoinitiator and additives were mixed evenly, defoamed, and cured under UV light for 5 minutes to prepare a low-shrinkage resin; the base resin was an epoxy resin (DGEBA, industrial grade, Yueyang Baling Petrochemical); the photoinitiator was triarylsulfonium hexafluoroantimonate (Chivacure 1176, Qitai Technology Co., Ltd.), and the amount of the photoinitiator added was 1.3 wt% of the base resin; the additive was a PVAc graft, and the amount of the additive added was 12 wt% of the base resin.

[0070] Example 2:

[0071] The only difference between this embodiment and embodiment 1 is that, in the preparation of the PVAc grafted product, the amount of the maleic anhydride-p-phenylenediamine derivative added is 28 wt % of the PVAc preliminary polymer.

[0072] Example 3:

[0073] The only difference between this embodiment and embodiment 2 is that, in the preparation of the low shrinkage resin, the amount of the additive added is 26 wt % of the base resin.

[0074] Example 4:

[0075] The present invention finds that, in the preparation of a low-shrinkage resin, the addition of an additive containing menthol salicylate and ZL-tert-butyl asparagine to the low-shrinkage resin further increases the gel fraction of the low-shrinkage resin, reduces the shrinkage rate of the low-shrinkage resin, and improves the thermal stability of the low-shrinkage resin. During use, the additive containing menthol salicylate and ZL-tert-butyl asparagine interacts with a polyvinyl alcohol (PVAc) graft, causing the PVAc graft to stretch. The menthol salicylate and ZL-tert-butyl asparagine also partially penetrate into the cross-linked structure of the PVAc graft, thereby enhancing the additive's stress-offsetting effect on the unsaturated resin during curing, effectively healing cracks, increasing the shrinkage rate of the low-shrinkage resin, improving the performance of the low-shrinkage resin, and simultaneously increasing the gel fraction and thermal stability of the low-shrinkage resin. Through research, it was found that when the content of menthol salicylate is 1-3wt% of the base resin and the content of ZL-tert-butyl asparagine is 0.5-4wt% of the base resin, better effects are achieved.

[0076] The only difference between this embodiment and embodiment 3 is that, in the preparation of the low shrinkage resin, the additives further contain menthol salicylate and ZL-tert-butyl asparagine, the content of menthol salicylate is 1.3 wt % of the base resin, and the content of ZL-tert-butyl asparagine is 1.4 wt % of the base resin.

[0077] Example 5:

[0078] The only difference between this embodiment and embodiment 3 is that, in the preparation of the low shrinkage resin, the additives further contain menthol salicylate and ZL-tert-butyl asparagine, the content of menthol salicylate is 2.3 wt % of the base resin, and the content of ZL-tert-butyl asparagine is 3.5 wt % of the base resin.

[0079] Example 6:

[0080] The only difference between this embodiment and embodiment 5 is that ZL-tert-butyl asparagine is not added to the additives during the preparation of the low shrinkage resin.

[0081] Example 7:

[0082] The only difference between this embodiment and embodiment 5 is that menthol salicylate is not added as an additive in the preparation of the low shrinkage resin.

[0083] Test Example 1:

[0084] 1. Infrared detection

[0085] Test samples: PVAc grafts and PVAc preliminary polymers prepared in Example 2.

[0086] Using KBr as dispersant, the test sample was mixed with an appropriate amount of KBr powder and ground evenly, then pressed into a sheet at 10 MPa and then subjected to infrared testing. The test range was 4000-500 cm -1 .

[0087] Infrared spectrum such as Figure 1 As shown, a is the PVAc primary polymer, b is the PVAc graft, and the infrared of the PVAc graft is compared with the infrared of the PVAc primary polymer at 3311 cm -1 The absorption peak of amide nitrogen and hydrogen appears at 1600 cm -1 1530cm -1 The peak at is the benzene ring absorption peak, indicating that the PVAc grafted product was successfully obtained.

[0088] 2. Molecular weight detection and molecular weight distribution

[0089] Test sample: PVAc preliminary polymer prepared in Examples 1-7.

[0090] The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the test samples were determined by gel permeation chromatography (GPC) equipped with a differential refractive index detector. GPC was performed using an autosampler, and the sample molecular weights were calculated based on commercially available PS standards. The test temperature was 40°C, with THF as the mobile phase at a flow rate of 0.35 m / min.

[0091] After testing, the number average molecular weight (Mn) of the PVAc preliminary polymers prepared in Examples 1-7 ranged from 2800 to 5900 g / mol, and the molecular weight distribution (Mw / Mn) ranged from 1.3 to 1.7. The number average molecular weight range refers to the minimum and maximum molecular weights obtained in the experimental tests, and the molecular weight distribution range refers to the minimum and maximum distribution values in the experimental tests.

[0092] Test Example 2:

[0093] 1. Compression shear strength

[0094] Test sample: PVAc grafted product prepared by the method of Example 1-2.

[0095] Test emulsion: The test sample PVAc grafted product was added to the emulsion, the content of the PVAc grafted product was 30 wt% of the emulsion; the emulsion contained 5 wt% of alkylethoxysulfosuccinic acid disodium salt and 0.5 wt% of sodium bicarbonate.

[0096] Test Material: Birch wood was used as the test piece for gluing and testing compressive shear strength. The bonding surface was smooth and free of dirt, with the main fiber direction parallel to the axis of the test piece. The test piece was 30mm long, 25mm wide, and 10mm thick.

[0097] Specimen Preparation: Apply the test emulsion evenly to the bonding surfaces of two test pieces, with an overlap area of 25mm x 25mm. Place the overlapped wood pieces in a fixture and apply constant pressure. Place them in an environment with a temperature of 25°C and a relative humidity of 60% for 24 hours. After removing the pressure, place them in the same environment for 48 hours before conducting the compression shear strength test. Perform at least three sets of tests.

[0098] Compression shear strength test: A universal mechanical testing machine was used, with the specimen failure load within 20%-80% of the full load. The beam descended at a speed of 2 mm / min. The test was conducted at an ambient temperature of 30°C and a relative humidity of 80%.

[0099] The compressive shear strength is calculated as follows:

[0100] σ=F / LB.

[0101] Where: σ is the compressive shear strength, unit: MPa; F is the maximum load when the specimen breaks, unit: N; L is the length of the overlapped part of the specimen, unit: mm; B is the width of the overlapped part of the specimen, unit: mm.

[0102] The compressive shear strength obtained in Example 1 is 10.95 MPa, and the compressive shear strength obtained in Example 2 is 13.24 MPa, indicating that the PVAc graft obtained in the present invention has good compressive shear strength after being used in emulsion for wood bonding.

[0103] 2. Dilution stability

[0104] Test sample: PVAc grafted product prepared by the method of Example 1-2.

[0105] Test emulsion: The test sample PVAc grafted product was added to the emulsion, the content of the PVAc grafted product was 30 wt% of the emulsion; the emulsion contained 5 wt% of alkylethoxysulfosuccinic acid disodium salt and 0.5 wt% of sodium bicarbonate.

[0106] Dilute the emulsion: dilute the test emulsion with distilled water to a mass fraction of 3%. Use a graduated cylinder to measure 100 ml of the diluted emulsion, cover it and let it stand for 72 hours. Observe the volume of the supernatant and the volume of the bottom sediment (ml). The volume fraction of the supernatant and sediment in the emulsion indicates its dilution stability. The larger the volume fraction, the worse the dilution stability. If no obvious stratification occurs, it means that the emulsion has good dilution stability.

[0107] After testing, the PVAc grafted products obtained in Example 1 and Example 2 were used in emulsions to obtain diluted emulsions. After standing for 72 hours, no stratification occurred, indicating good dilution stability.

[0108] Test Example 3:

[0109] 1. Determination of gel fraction

[0110] Test sample: low shrinkage resin prepared in each example.

[0111] Test method: Pour acetone into a Soxhlet extractor, take a test sample of about 0.5-1.0g, record the mass as m1, place it in the Soxhlet extractor and extract for 24 hours, and finally dry it to constant weight. Take out the extracted test sample and place it in a 50℃ oven to dry for 6 hours to constant weight, record its mass as m2.

[0112] The gel fraction of low shrinkage resin can be obtained according to the following formula:

[0113] Gel fraction = m2 / m1×100%.

[0114] The test results of the gel fraction of low shrinkage resin are as follows: Figure 2 As shown, the gel rate of Example 1 is 79.53%, and the gel rate of Example 2 is 81.37%. Compared with Example 1, Example 2 shows that after more maleic anhydride-p-phenylenediamine derivatives are introduced into the PVAc graft, the gel rate of the low shrinkage resin prepared is higher; the gel rate of Example 3 is 83.62%. Compared with Example 2, Example 3 shows that the higher the amount of PVAc graft is used, the higher the gel rate of the low shrinkage resin prepared is; the gel rate of Example 4 is 85.14%. Compared with Example 3, Example 4 shows that menthol water The use of salicylate and ZL-tert-butyl asparagine further improves the gel fraction of the low-shrinkage resin. The gel fraction of Example 5 is 86.36%. Compared with Example 3, Example 4 shows that increasing the amount of menthol salicylate and ZL-tert-butyl asparagine can improve the gel fraction of the low-shrinkage resin. Compared with Examples 6-7, Example 5 shows that the combined use of menthol salicylate and ZL-tert-butyl asparagine has a better effect on improving the gel fraction of the low-shrinkage resin than the separate use of menthol salicylate or ZL-tert-butyl asparagine.

[0115] 2. Determination of shrinkage

[0116] Test sample: low shrinkage resin prepared in each example.

[0117] Test method: Apply a release agent to a rectangular mold measuring 100 mm (L x W x H) x 10 mm (H x W) x 1 mm (H x H). Pour the resin solution obtained according to the methods of the various examples into the mold and completely cure it under a UV lamp. Remove the cured resin and measure its length. Calculate the linear shrinkage using the following formula.

[0118] Linear shrinkage = (100 - length after curing) / 100 × 100%.

[0119] The test results of linear shrinkage of low shrinkage resin are as follows: Figure 3 As shown, the linear shrinkage of Example 1 is 1.22%, and the linear shrinkage of Example 2 is 1.15%. Compared with Example 1, Example 2 shows that after more maleic anhydride-p-phenylenediamine derivatives are introduced into the PVAc graft, the linear shrinkage of the low-shrinkage resin prepared is reduced; the linear shrinkage of Example 3 is 1.09%. Compared with Example 2, Example 3 shows that the higher the amount of PVAc graft is used, the smaller the linear shrinkage of the low-shrinkage resin prepared; the linear shrinkage of Example 4 is 1.01%. Compared with Example 3, Example 4 shows that menthol salicylic acid The use of menthol salicylate and ZL-tert-butyl asparagine further reduces the linear shrinkage of the low-shrinkage resin; the linear shrinkage of Example 5 is 0.93%. Compared with Example 3, Example 4 shows that increasing the amount of menthol salicylate and ZL-tert-butyl asparagine can reduce the linear shrinkage of the obtained low-shrinkage resin; compared with Examples 6-7, Example 5 shows that the combined use of menthol salicylate and ZL-tert-butyl asparagine has a better effect on reducing the linear shrinkage of the low-shrinkage resin than the separate use of menthol salicylate or ZL-tert-butyl asparagine.

[0120] 3. Thermal stability

[0121] Test sample: low shrinkage resin prepared in each example.

[0122] Thermogravimetric analysis (TGA): 2-3 mg of the test sample was placed in a sealed cell of a thermogravimetric analyzer. The epoxy resin system was subjected to thermogravimetric analysis at a heating rate of 10°C / min from 20-700°C in a dynamically dried high-purity nitrogen atmosphere.

[0123] The mass of the low shrinkage resin does not change substantially before 250°C. When the temperature reaches 350°C, the mass loss of the low shrinkage resin obtained in each embodiment does not exceed 4.6%. When the temperature reaches 400°C, the mass loss of the low shrinkage resin obtained in each embodiment does not exceed 47%.

[0124] The above embodiments are intended to illustrate the present invention only and are not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the scope of patent protection of the present invention shall be defined by the claims.

Claims

1. A low shrinkage resin comprising: The invention is prepared from a base resin and an additive, wherein the base resin is an epoxy resin, the additive includes a PVAc graft, and the PVAc graft includes a PVAc segment and a graft segment bonded thereto; the content of the graft segment is less than 26.47 wt%; In the preparation of the PVAc grafted compound, a maleic anhydride-p-phenylenediamine derivative and a PVAc preliminary polymer are prepared under the action of an initiator. The maleic anhydride-p-phenylenediamine derivative is synthesized from maleic anhydride and p-phenylenediamine, and the PVAc preliminary polymer is obtained by preliminary polymerization of VAc under the action of a composite initiator. The grafted material is a maleic anhydride-p-phenylenediamine derivative, a cross-linked structure exists in the PVAc grafted material, and the number average molecular weight of the PVAc segment in the PVAc grafted material is greater than 2500 g / mol; The additives further include menthol salicylate and ZL-asparagine tert-butyl ester. The content of menthol salicylate is 1-3wt% of the base resin, and the content of ZL-asparagine tert-butyl ester is 0.5-4wt% of the base resin.

2. A low shrinkage resin according to claim 1, characterized in that: The content of the PVAc grafted product is greater than 5.93%.

3. A low shrinkage resin according to claim 1, characterized in that: The linear shrinkage of the low-shrinkage resin is less than 1.25%.

4. The method for preparing a low shrinkage resin according to claim 1, comprising: Maleic anhydride-p-phenylenediamine derivatives can be synthesized from maleic anhydride and p-phenylenediamine; VAc is preliminarily polymerized under the action of a composite initiator to obtain a PVAc preliminarily polymer; The PVAc grafted product is prepared by reacting a maleic anhydride-p-phenylenediamine derivative with a PVAc preliminary polymer under the action of an initiator; The low shrinkage resin is prepared by placing a base resin, a photoinitiator and an additive under ultraviolet light conditions. The additive is a PVAc grafted product and further comprises menthol salicylate and ZL-asparagine tert-butyl ester.

5. The method for preparing a low shrinkage resin according to claim 4, wherein: The composite initiator is azobisisobutyronitrile and 1,1'-azo(cyanocyclohexane).

6. The method for preparing a low shrinkage resin according to claim 4, wherein: The amount of maleic anhydride added is 1.82 times or more of the amount of p-phenylenediamine added.

7. The method for preparing a low shrinkage resin according to claim 4, wherein: The amount of the maleic anhydride-p-phenylenediamine derivative added is 12-36 wt % of the PVAc preliminary polymer.

8. The method for preparing a low shrinkage resin according to claim 4, wherein: The additive is added in an amount of 8-32 wt % of the base resin.

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