An unsaturated polyester resin for resin diamond and a method for preparing the same

Abstract

An unsaturated polyester resin for diamond resin and its preparation method are disclosed, belonging to the technical field of polyester resins. It is composed of the following components: maleic anhydride, DCPD, DEG, EG, antioxidant, polymerization inhibitor, paraffin wax, styrene, composite accelerator, and water; the composite accelerator is composed of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in a weight ratio of 1:2 to 4:6. The preparation steps are: 1) Add maleic anhydride, DEG, antioxidant, and water; heat and add DCPD, maintaining the temperature; 2) Add EG, MA, DEG, antioxidant, and polymerization inhibitor; heat and react; 3) Cool and add polymerization inhibitor and paraffin wax; cool and add styrene and the composite accelerator to obtain the unsaturated polyester resin for diamond resin; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in a weight ratio of 1:2 to 4:6 at 25 to 60°C. This invention features excellent mechanical properties, good air-drying properties, high solids content, and low linear shrinkage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyester resin, and particularly relates to an unsaturated polyester resin for resin diamond and a preparation method thereof. BACKGROUND

[0002] In the field of ornaments, resin diamonds are often used in the production of various types of jewelry such as necklaces, earrings, and bracelets to add brilliance to the appearance of the wearer. In the field of artware, whether it is delicate ornaments, pendants, or customized artware with commemorative significance, resin diamonds can be seen everywhere, giving artware a unique aesthetic appeal. In the decoration material industry, resin diamonds are widely used in wall decoration, furniture inlay, holiday decoration, and gift packaging. The reason why resin diamonds play an important role in these fields is due to their appearance and production cost advantages. In terms of appearance, through exquisite processing, they can achieve a refractive effect and glossiness that is very close to that of natural diamonds, making it difficult to distinguish between the two. In terms of cost, the raw materials are easy to obtain and the processing flow is relatively simple, and the price is much lower than that of natural diamonds, greatly reducing the production cost of related products.

[0003] As the core matrix material for preparing resin diamonds, the performance of unsaturated polyester resin plays a decisive role in the quality of resin diamonds, as it directly affects the hardness of resin diamonds and determines whether they are resistant to wear and tear in daily use. The performance of unsaturated polyester resin directly determines whether resin diamonds can meet the market's demand for high-quality products. Unsaturated polyester resin is a thermosetting resin made by condensation polymerization of unsaturated diacid, saturated diacid, and dihydric alcohol.

[0004] Currently, the unsaturated polyester resin used for resin diamonds has the problems of poor mechanical properties, poor air dryness, low solid content, and high linear shrinkage rate in actual application. Poor mechanical properties can cause scratches and loss of luster, edge collapse and fragmentation during processing, high scrap rate, and low efficiency. Poor air dryness can cause the surface of the cured product to be sticky and prone to contamination, making it difficult to process normally, and increasing the cost of batch production. Low solid content leads to low raw material forming rate, cost waste, loose structure of finished products, easy damage, insufficient gloss and color, and easy water absorption and deterioration. High linear shrinkage rate can cause dimensional distortion and stress concentration after curing, low yield, difficult assembly, and appearance defects, resulting in a decrease in aesthetic appeal and market acceptance. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide an unsaturated polyester resin for resin diamonds and a preparation method thereof. The present application has the characteristics of excellent mechanical properties, good air dryness, high solid content, and low linear shrinkage rate.

[0006] To achieve the above object, the present application provides an unsaturated polyester resin for resin diamond, which is composed of the following components in parts by weight: maleic anhydride 620-680 parts, dicyclopentadiene 285-540 parts, diethylene glycol 124-500 parts, ethylene glycol 60-320 parts, first antioxidant 0.29-0.45 parts, second antioxidant 0.29-0.45 parts, first polymerization inhibitor 0.08-0.22 parts, second polymerization inhibitor 0.14-0.19 parts, paraffin wax 0.93-1.07 parts, styrene 360-495 parts, composite accelerator 19-23 parts, and water 97-103 parts; the molar ratio of unsaturated acid to dicyclopentadiene is 1.55-3.00:1; the molar ratio of total alcohol to total acid is 1.15-1.29:1; and the composite accelerator is composed of cobalt iso-octoate, copper iso-octoate and potassium iso-octoate in a weight ratio of 1:2-4:6.

[0007] The molar ratio of unsaturated acid to dicyclopentadiene in the present application is 1.55-3.00:1; the molar ratio of unsaturated acid to dicyclopentadiene affects the reactivity, curing result and mechanical property; when the molar ratio of unsaturated acid to dicyclopentadiene is too low, the resin curing speed is slow, the crosslinking density is low, the curing degree is insufficient, and the mechanical property of the resin is low; and when the molar ratio of unsaturated acid to dicyclopentadiene is too high, the resin gel speed is fast, the molecular diffusion is blocked, the residual unreacted double bond is needed to be post-cured to improve the crosslinking degree, and local defects are caused due to uneven curing.

[0008] The molar ratio of total alcohol to total acid in the present application is 1.15-1.29:1; the ratio range in the present application can optimize the molecular chain structure of the unsaturated polyester resin for resin diamond, improve the resin curing uniformity, introduce long-chain diethylene glycol into the polyester main chain, improve the molecular chain flexibility, and reduce the rigid shrinkage; and the excess alcohol in the molar ratio of total alcohol to total acid in the present application is to make both ends of the polyester molecular chain be hydroxyl groups in the early stage and avoid the polyester molecular weight being too large; the lower the molar ratio of total alcohol to total acid, the more difficult it is to form macromolecules in the system, and the smaller the synthesized unsaturated polyester resin molecules; but the excess hydroxyl group is too much, the polymerization degree is reduced, the molecular weight is small, the polyester molecules contain less unsaturated double bonds, part of the alcohol in the product does not participate in the reaction, and the resin performance is affected, resulting in high shrinkage rate and poor toughness of the resin diamond. Appropriately increasing the hydroxyl group concentration can increase the reactivity, improve the polymer molecular weight, make the gel and surface drying time shorter, and improve the mechanical property.

[0009] Preferably, the molar ratio of unsaturated acid to dicyclopentadiene is 1.61-2.04:1; in the ratio range, the resin curing speed is faster, the gel time is shortened, the resin crosslinking rate and crosslinking density are balanced, and the curing efficiency and mechanical property can be considered.

[0010] Preferably, the molar ratio of total alcohol to total acid is 1.16~1.22:1; this can further improve curing performance, make the reaction more stable, and reduce local defects; it can more effectively improve the flexibility of the molecular chain; it optimizes the distribution of hydroxyl groups at both ends of the molecular chain, resulting in more balanced reactivity, moderate degree of polymerization, and ensuring suitable resin viscosity.

[0011] The first and second antioxidants are 2,6-di-tert-butyl-4-methylphenol or triphenyl phosphite; 2,6-di-tert-butyl-4-methylphenol can effectively capture free radicals, and 2,6-di-tert-butyl-4-methylphenol is abbreviated as BHT. Triphenyl phosphite can decompose hydrogen peroxide, thereby preventing or delaying the oxidation of the resin matrix.

[0012] The first and second polymerization inhibitors are methylhydroquinone, 4-tert-butylcatechol, or hydroquinone. Both the first and second polymerization inhibitors of the present invention can prolong the gelation time and storage period, and prevent or slow down the premature gelation of the resin in high-temperature processes and storage.

[0013] The composite accelerator of this invention is composed of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in a weight ratio of 1:2 to 4:6. The potassium ions in the composite accelerator have a synergistic effect with cobalt ions, significantly improving free radical initiation efficiency, thus accelerating initiation and reducing the amount of cobalt required. Potassium isooctanoate facilitates the chelation of active metals with polymers, exhibiting strong promoting and drying properties, accelerating curing time. In practical applications, when used in conjunction with cobalt, it can serve as a colorless accelerator for unsaturated polyester and fiberglass resin diamonds, improving the color and transparency of the resin diamonds. Potassium ions can also activate peroxides, accelerating their decomposition and generating more free radicals, thereby shortening gel time and curing cycle. Copper isooctanoate optimizes the initiation efficiency of cobalt ions through a potential gradient and ensures its own activity and distribution with the coordination and dispersion effect of potassium ions. The composite accelerator of this invention improves the air-drying performance of resin diamonds, achieving rapid demolding and improving product color, meeting the requirements for resin diamond transparency, while also reducing costs.

[0014] Preferably, the composite accelerator is composed of cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:2.7 to 3.3:6.

[0015] At the optimal ratio, the synergistic effect of potassium and cobalt ions is superior, which can better improve the decomposition efficiency of peroxides, generate more active free radicals, and further accelerate the initiation rate. At the same time, it can further reduce the amount of cobalt used while ensuring initiation efficiency, reducing the risk of diamond resin coloration caused by excessive cobalt ions. At the optimal ratio, the drying performance of the composite accelerator is more coordinated, and the air-drying properties of the resin surface are better improved.

[0016] This invention also provides a method for preparing an unsaturated polyester resin for use with diamond resins, comprising the following steps:

[0017] (1) Weigh out a portion of maleic anhydride, a portion of diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. After heating to 110~120℃, add dicyclopentadiene and keep warm for 1~2h.

[0018] (2) Weigh out the ethylene glycol, the remaining maleic anhydride, the remaining diethylene glycol, the second antioxidant and the first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 195~198℃ and react until the acid value reaches 25~35mgKOH / g.

[0019] (3) Cool the product obtained in step (2) to 175~185℃, add the second polymerization inhibitor and paraffin; cool to ≤60℃, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:2~4:6 at 25~60℃.

[0020] In step (1), the amount of maleic anhydride added accounts for 73.5~83.9% of the total amount of maleic anhydride added, and in step (2), the amount of maleic anhydride added accounts for 16.1~26.5% of the total amount of maleic anhydride added; in step (1), the amount of diethylene glycol added accounts for 11.2~50.0% of the total amount of diethylene glycol added, and in step (2), the amount of diethylene glycol added accounts for 50.0~88.8% of the total amount of diethylene glycol added.

[0021] The specific operation of step (1) is to weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them into the reaction vessel. Under inert gas conditions, heat to 110~120℃ and then add dicyclopentadiene at a rate of 100~150ml / h and keep warm for 1~2h.

[0022] After heating to 110~120℃ in step (1), dicyclopentadiene is added to prevent the violent self-polymerization of DCPD and ensure production safety. In addition, it can also generate a DCPD-maleic acid half ester intermediate with a well-defined structure. This intermediate directly lays the specific molecular structure basis for the subsequent synthesis of resin, controls the reaction process and product structure, and makes the resin diamond have excellent physical properties, chemical stability and processing characteristics.

[0023] In unsaturated polyester molecular chains, the distribution of unsaturated double bonds is crucial to resin performance. If all maleic anhydride is added to the reaction system at once, the maleic anhydride is prone to self-polymerization, resulting in unsaturated double bond enrichment regions and saturated segments in the molecular chains. This leads to an uneven network structure after resin curing, affecting the final mechanical properties. In step (1), saturated and unsaturated acids participate in polycondensation relatively evenly, generating a prepolymer with unsaturated double bonds distributed at intervals on the molecular chains, whose structure is relatively regular. In step (2), the remaining maleic anhydride is added. This maleic anhydride mainly connects to the ends of the prepolymer chains or inserts into existing chain segments. Through this stepwise feeding method, the distribution of unsaturated double bonds in the final resin molecular chains will be more uniform than that of adding them in one step. When the double bonds are evenly distributed, after copolymerization and curing with styrene, a three-dimensional network structure with uniform crosslinking points and fewer defects is formed, which not only achieves better mechanical properties but also reduces the occurrence of side reactions.

[0024] The first polymerization inhibitor is added in step (2) to prevent the system from gelling, to suppress the uncontrolled polymerization reaction in time, and to avoid gelling due to excessive polymerization and excessive cross-linking of molecular chains during the reaction.

[0025] If the reaction in step (2) continues until the acid value is higher than 35 mg KOH / g, the polycondensation reaction has not proceeded to the intended extent. The resin molecular chains are short, the molecular weight is low, the mechanical strength after curing is poor, and the reactivity is abnormal. If the reaction in step (2) continues until the acid value is lower than 25 mg KOH / g, unnecessary side reactions will occur, which will bring the risk of gelation, and will also lead to a decrease in the toughness and impact strength of the product, as well as a reduction in compatibility with styrene.

[0026] The specific operation of step (3) is to cool the product obtained in step (2) to 175~185℃, add the second polymerization inhibitor and paraffin; cool to ≤60℃, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:2~4:6 at 25~60℃.

[0027] Premixing of the composite accelerator is a crucial step in ensuring its synergistic effect, curing uniformity, and the performance of the resin diamond. It effectively avoids curing defects and performance degradation caused by non-premixing, and is an essential process for achieving superior resin diamond performance. After premixing, the three components are evenly distributed. Potassium ions can efficiently interact with cobalt ions, increasing the decomposition rate of peroxides, generating more active free radicals, and shortening gel time and curing cycle. Simultaneously, the synergistic effect of copper isooctanoate is more stable, preventing excessive local curing. The premixed accelerator is more evenly dispersed in the resin, avoiding excessively high or low local concentrations, reducing internal stress caused by differences in curing rates, and minimizing defects such as cracking and uneven shrinkage in the resin diamond. The uniform distribution of cobalt ions prevents resin coloration caused by excessively high local concentrations. Combined with the colorless accelerating properties of potassium isooctanoate, it significantly improves the transparency of the resin diamond. The potassium ions in potassium isooctanoate have a synergistic effect on cobalt ions. It helps maintain cobalt ions in a more active state, thereby accelerating initiation efficiency. This means that to achieve the same gel and curing speed, the amount of expensive cobalt isooctanoate, which can affect the color of the product, can be significantly reduced, helping to control costs.

[0028] The resin diamond prepared in step (3) is placed at 23~26℃ for 20~30 min and the liquid state changes to the gel state.

[0029] The stirring speed in steps (1), (2) and (3) is 180~220 r / min.

[0030] The application of the unsaturated polyester resin of this invention is specifically its application in the preparation of simulated diamond jewelry and diamond crafts.

[0031] The application of the unsaturated polyester resin of the present invention includes the following steps: adding an initiator to the unsaturated polyester resin of the present invention, stirring evenly, pouring into a steel mold with dimensions of 350mm×300mm×5mm, and curing at 21~25℃ for 24h to obtain an unsaturated polyester resin casting.

[0032] The initiator is used at a weight percentage of 2% of the unsaturated polyester resin. The initiator is methyl ethyl ketone peroxide. The initiator dosage is 2% of the unsaturated polyester resin by weight.

[0033] Compared with the prior art, the beneficial effects of this invention are:

[0034] 1. This invention features excellent mechanical properties, good air-drying properties, high solids content, and low linear shrinkage. The composite accelerator, formulated in a specific ratio, achieves a more uniform and stable curing effect through synergistic effects, improving air-drying and demolding efficiency. The molar ratio of unsaturated to saturated acids ensures that the polyester molecular chains are hydroxyl groups at both ends, solving the problem of poor casting fluidity caused by excessive molecular weight and avoiding the defect of poor toughness caused by excessive hydroxyl groups. Simultaneously, the introduction of diethylene glycol further enhances the flexibility of the molecular chains, improving the impact resistance of the resin diamond. Using the molar ratio of unsaturated to saturated acids and the molar ratio of total alcohol to total acid in this invention increases the curing speed, achieving a balance between curing efficiency and resin diamond performance. The casting of this invention has a tensile strength of 40.55~70.46 MPa, a tensile modulus of elasticity of 1869~3890 MPa, an elongation at break of 2.67~7.63%, a flexural strength of 40.74~95.40 MPa, a flexural modulus of elasticity of 1538~3525 MPa, an impact strength of 4.04~7.54 kJ / m², a Barcol hardness of 19~35 HBa, a linear shrinkage rate of 1.24~2.52%, and a solid content of 75.6~79.5%.

[0035] 2. The present invention controls the rate of addition of dicyclopentadiene and reacts under inert gas protection, which is beneficial to improving the mechanical properties of the resin diamond; at the same time, the inert gas isolates oxygen, reduces oxidation side reactions, and makes the molecular chain structure of the unsaturated polyester resin more regular. Detailed Implementation

[0036] Example 2 is the preferred embodiment of the present invention. The present invention will be further described below with reference to specific embodiments and comparative examples.

[0037] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows:

[0038] maleic anhydride: purchased from Wanhua Chemical Group Petrochemical Sales Co., Ltd.;

[0039] Dicyclopentadiene: purchased from Zibo Baochi Trade Co., Ltd.;

[0040] Diethylene glycol: purchased from Changzhou Chemical and Light Industry Materials Corporation;

[0041] Ethylene glycol: purchased from Lijin Leo Chemical Co., Ltd.;

[0042] Triphenyl phosphite: purchased from Jiangsu Evergreen New Material Technology Co., Ltd.

[0043] BHT: Purchased from Changzhou Yurong Chemical Co., Ltd.;

[0044] Methylhydroquinone: purchased from Changzhou Yurong Chemical Co., Ltd.;

[0045] p-tert-butylcatechol: purchased from Changzhou Yurong Chemical Co., Ltd.;

[0046] Hydroquinone: Purchased from Changzhou Yurong Chemical Co., Ltd.;

[0047] Paraffin wax, type 58: purchased from Jingmen Weijia Industrial Co., Ltd.;

[0048] Styrene: Purchased from Shenyang Jinhua Petrochemical Co., Ltd.;

[0049] Cobalt isooctanoate, model EC-12: purchased from J.P. Chemical (Shanghai) Co., Ltd.;

[0050] Copper isooctanoate, model ZECU-8: purchased from Jeppy Chemicals (Shanghai) Co., Ltd.;

[0051] Potassium isooctanoate: purchased from Qingdao Yousuo Chemical Technology Co., Ltd.;

[0052] Methyl ethyl ketone peroxide, model V388: purchased from Qingdao Feiyang Trading Co., Ltd.;

[0053] The water is deionized.

[0054] Table 1. Raw materials for the embodiments (by weight).

[0055] .

[0056] Example 1

[0057] The preparation method in this embodiment adopts the following steps:

[0058] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 115°C and then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite. The stirring speed is 180 r / min.

[0059] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, second antioxidant and first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 197°C and react until the acid value reaches 30 mg KOH / g. The second antioxidant is triphenyl phosphite and the first polymerization inhibitor is methyl hydroquinone. The stirring speed is 200 r / min.

[0060] (3) Cool the product obtained in step (2) to 180°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:2:6 at 35°C; the second polymerization inhibitor is methylhydroquinone; the stirring speed is 220r / min.

[0061] Example 2

[0062] The preparation method in this embodiment adopts the following steps:

[0063] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 115°C and then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite. The stirring speed is 185 r / min.

[0064] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, second antioxidant and first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 197°C and react until the acid value reaches 30 mg KOH / g. The second antioxidant is triphenyl phosphite and the first polymerization inhibitor is methyl hydroquinone. The stirring speed is 195 r / min.

[0065] (3) Cool the product obtained in step (2) to 180°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:3:6 at 35°C; the second polymerization inhibitor is methylhydroquinone; the stirring speed is 215r / min.

[0066] Example 3

[0067] The preparation method in this embodiment adopts the following steps:

[0068] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 115°C and then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite. The stirring speed is 180 r / min.

[0069] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, second antioxidant and first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 197°C and react until the acid value reaches 30 mg KOH / g. The second antioxidant is triphenyl phosphite and the first polymerization inhibitor is methyl hydroquinone. The stirring speed is 200 r / min.

[0070] (3) Cool the product obtained in step (2) to 180°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:4:6 at 35°C; the second polymerization inhibitor is methylhydroquinone; the stirring speed is 220r / min.

[0071] Example 4

[0072] The preparation method in this embodiment adopts the following steps:

[0073] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 115°C and then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite. The stirring speed is 180 r / min.

[0074] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, second antioxidant and first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 197°C and react until the acid value reaches 30 mg KOH / g. The second antioxidant is triphenyl phosphite and the first polymerization inhibitor is methyl hydroquinone. The stirring speed is 200 r / min.

[0075] (3) Cool the product obtained in step (2) to 180°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:3:6 at 35°C; the second polymerization inhibitor is methylhydroquinone; the stirring speed is 220r / min.

[0076] Example 5

[0077] The preparation method in this embodiment adopts the following steps:

[0078] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 115°C and then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite. The stirring speed is 180 r / min.

[0079] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, second antioxidant and first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 197°C and react until the acid value reaches 30 mg KOH / g. The second antioxidant is triphenyl phosphite and the first polymerization inhibitor is methyl hydroquinone. The stirring speed is 200 r / min.

[0080] (3) Cool the product obtained in step (2) to 180°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:3:6 at 35°C; the second polymerization inhibitor is methylhydroquinone; the stirring speed is 220r / min.

[0081] Example 6

[0082] The preparation method in this embodiment adopts the following steps:

[0083] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 110°C and then add dicyclopentadiene at a rate of 100 ml / h and keep warm for 1 h. The first antioxidant is triphenyl phosphite. The stirring speed is 180 r / min.

[0084] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, the second antioxidant and the first polymerization inhibitor according to the weight parts and add them to the reaction vessel of step (1). Heat to 195°C and react until the acid value reaches 25 mg KOH / g. The second antioxidant is 2,6-di-tert-butyl-4-methylphenol and the first polymerization inhibitor is methylhydroquinone. The stirring speed is 200 r / min.

[0085] (3) Cool the product obtained in step (2) to 175°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:2.7:6 at 25°C; the second polymerization inhibitor is hydroquinone; the stirring speed is 220r / min.

[0086] Example 7

[0087] The preparation method in this embodiment adopts the following steps:

[0088] (1) Weigh maleic anhydride, diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. Under inert gas conditions, heat to 120°C and then add dicyclopentadiene at a rate of 150 ml / h and keep warm for 2 h. The first antioxidant is 2,6-di-tert-butyl-4-methylphenol. The stirring speed is 180 r / min.

[0089] (2) Weigh out ethylene glycol, maleic anhydride, diethylene glycol, second antioxidant and first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 198°C and react until the acid value reaches 35 mg KOH / g. The second antioxidant is 2,6-di-tert-butyl-4-methylphenol and the first polymerization inhibitor is methylhydroquinone. The stirring speed is 200 r / min.

[0090] (3) Cool the product obtained in step (2) to 185°C, add the second polymerization inhibitor and No. 58 paraffin; cool to ≤60°C, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond; the composite accelerator is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:3.3:6 at 60°C; the second polymerization inhibitor is 4-tert-butylcatechol; the stirring speed is 220r / min.

[0091] Comparative Example 1

[0092] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the formulation is different. The formulation of this comparative example is shown in Table 2.

[0093] Comparative Example 2

[0094] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the formulation is different. The formulation of this comparative example is shown in Table 2.

[0095] Comparative Example 3

[0096] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the composite accelerator in step (3) is composed of 5.25 parts of cobalt isooctanoate and 15.75 parts of copper isooctanoate. The formulation of this comparative example is shown in Table 2.

[0097] Comparative Example 4

[0098] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the composite accelerator in step (3) is composed of 3 parts cobalt isooctanoate and 18 parts potassium isooctanoate. The formulation of this comparative example is shown in Table 2.

[0099] Comparative Example 5

[0100] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the molar ratio of unsaturated acid to saturated acid is too low. The formulation of this comparative example is shown in Table 2.

[0101] Comparative Example 6

[0102] The preparation method of the unsaturated polyester resin for diamond resin described in this comparative example is the same as that in Example 2, except that the molar ratio of unsaturated acid to saturated acid is too high. The formulation of this comparative example is shown in Table 2.

[0103] Comparative Example 7

[0104] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the molar ratio of total alcohol to total acid is too low. The formulation of this comparative example is shown in Table 3.

[0105] Comparative Example 8

[0106] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the molar ratio of total alcohol to total acid is too high. The formulation of this comparative example is shown in Table 3.

[0107] Comparative Example 9

[0108] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the amount of composite accelerator in step (3) is different. The formulation of this comparative example is shown in Table 3.

[0109] Comparative Example 10

[0110] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the amount of composite accelerator in step (3) is different. The formulation of this comparative example is shown in Table 3.

[0111] Comparative Example 11

[0112] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the composite accelerator in step (3) is composed of cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:1:6. The formulation of this comparative example is shown in Table 3.

[0113] Comparative Example 12

[0114] The preparation method of the unsaturated polyester resin for resin diamond described in this comparative example is the same as that in Example 2, except that the composite accelerator in step (3) is composed of cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:5:6. The formulation of this comparative example is shown in Table 3.

[0115] Comparative Example 13

[0116] The formulation of the unsaturated polyester resin for diamond described in this comparative example is the same as that in Example 2, except that maleic anhydride and diethylene glycol are added in step (1).

[0117] Preparation method of step (1):

[0118] Weigh out maleic anhydride, diethylene glycol, the first antioxidant, and water according to the weight ratio and add them to the reaction vessel. Under inert gas conditions, heat to 115°C, then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite.

[0119] Comparative Example 14

[0120] The formulation of the unsaturated polyester resin for diamond described in this comparative example is the same as that in Example 2, except that dicyclopentadiene is added after heating to 100°C in step (1).

[0121] Preparation method of step (1):

[0122] Weigh out maleic anhydride, diethylene glycol, the first antioxidant, and water according to the weight ratio and add them to the reaction vessel. Under inert gas conditions, heat to 100°C, then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite.

[0123] Comparative Example 15

[0124] The formulation of the unsaturated polyester resin for diamond described in this comparative example is the same as that in Example 2, except that dicyclopentadiene is added after heating to 130°C in step (1).

[0125] Preparation method of step (1):

[0126] Weigh out maleic anhydride, diethylene glycol, the first antioxidant, and water according to the weight ratio and add them to the reaction vessel. Under inert gas conditions, heat to 130°C, then add dicyclopentadiene at a rate of 130 ml / h and keep warm for 1.5 h. The first antioxidant is triphenyl phosphite.

[0127] Comparative Example 16

[0128] The formulation of the unsaturated polyester resin for diamond described in this comparative example is the same as that in Example 2, except that the composite accelerator was not premixed in step (3).

[0129] Preparation method of step (3):

[0130] The product obtained in step (2) was cooled to 180°C, and the second polymerization inhibitor and No. 58 paraffin were added; the temperature was cooled to ≤60°C, and styrene and composite accelerator were added; the mixture was stirred to obtain unsaturated polyester resin for resin diamond; the composite accelerator was composed of cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:3:6; the composite accelerator was not premixed; the second polymerization inhibitor was methylhydroquinone.

[0131] Table 2 shows the raw materials (by weight) for Comparative Examples 1-6.

[0132] .

[0133] Table 3 shows the raw materials (by weight) for Comparative Examples 7-13.

[0134] .

[0135] Performance testing

[0136] The unsaturated polyester resins prepared in the examples and comparative examples were subjected to performance tests. The specific test results are shown in Tables 4, 5 and 6.

[0137] Preparation of the casting: 2% initiator was added to the unsaturated polyester resin obtained in the examples and comparative examples, stirred evenly, and poured into a steel mold with dimensions of 350mm×300mm×5mm. After curing at 21~25℃ for 24h, an unsaturated polyester resin casting was obtained. The initiator was methyl ethyl ketone peroxide.

[0138] Tensile strength was tested in accordance with GB / T2567-2021;

[0139] The tensile modulus of elasticity was tested in accordance with GB / T2567-2021;

[0140] The elongation at break was tested in accordance with GB / T2567-2021;

[0141] Bending strength was tested in accordance with GB / T2567-2021;

[0142] The flexural modulus of elasticity was tested in accordance with GB / T2567-2021;

[0143] Impact strength was tested in accordance with GB / T2567-2021;

[0144] Barcol hardness was tested according to GB / T3854-2017;

[0145] Linear shrinkage rate was tested according to ASTM D6289;

[0146] Solid content was tested in accordance with GB / T7193-2008;

[0147] Air dryness was tested according to the finger test method in GB / T1728-1979.

[0148] Table 4 Performance test results of castings from Examples 1-7

[0149] .

[0150] Table 5. Performance test results of the castings from Comparative Examples 1-8

[0151] .

[0152] Table 6. Performance test results of the castings of Comparative Examples 9-16

[0153] .

[0154] The unsaturated polyester resin for resin diamonds of this invention features excellent mechanical properties, good air-drying properties, high solids content, and low linear shrinkage. In Comparative Example 1, the component amounts in the formulation exceed the limits specified in this invention, preventing the resin molecular chain structure from forming a regular cross-linked network. This results in a significant decrease in mechanical properties, air-drying properties, and solids content, completely failing to meet the strength, toughness, and surface drying requirements of resin diamonds. Comparative Example 2 fails to form an optimized molecular chain structure, resulting in mechanical properties that do not meet the requirements for resin diamonds, and both air-drying properties and solids content are substandard. Comparative Example 3 lacks potassium isooctanoate, failing to leverage the synergistic effect of potassium isooctanoate, copper isooctanoate, and cobalt isooctanoate. This leads to insufficient curing and uneven cross-linking of the unsaturated polyester resin for resin diamonds, deteriorating mechanical properties, increased shrinkage, and loss of air-drying properties. Comparative Example 4, lacking the addition of copper isooctanoate, failed to leverage the synergistic effect of potassium isooctanoate, copper isooctanoate, and cobalt isooctanoate. This resulted in poor curing uniformity of the resin diamond using unsaturated polyester resin, decreased mechanical properties, increased shrinkage, and poor air-drying properties, failing to meet the performance requirements of the resin diamond. The composite accelerator of this invention, formulated in a specific ratio, achieves a more uniform and stable curing effect through synergistic effects, improving air-drying properties and demolding efficiency, while simultaneously reducing the color of the resin diamond.

[0155] In Comparative Example 5, the excessively low molar ratio of unsaturated acid to saturated acid resulted in slow resin curing speed, insufficient crosslinking density, low degree of curing, and the inability of the molecular chains to form a strong crosslinking network, leading to significant deterioration of mechanical properties and insufficient hardness, completely failing to meet the strength requirements of the resin diamond. In Comparative Example 6, the excessively high molar ratio of unsaturated acid to saturated acid resulted in excessively high resin crosslinking density, excessively rigid molecular chains, and increased shrinkage, making the resin diamond prone to cracking and deformation during curing, failing to balance strength and dimensional stability. In Comparative Example 7, the excessively low molar ratio of total alcohol to total acid led to abnormal polymerization degree of the polyester molecular chains, failing to effectively introduce the flexibility of diethylene glycol, resulting in irregular molecular chain structure, deterioration of mechanical properties, increased shrinkage, and incomplete curing reaction, leading to poor air-drying properties. In Comparative Example 8, the excessively high molar ratio of total alcohol to total acid led to a decrease in the polymerization degree of the polyester molecular chains, a smaller molecular weight, a reduced number of unsaturated double bonds in the molecular chains, insufficient crosslinking density after curing, deterioration of mechanical properties, increased shrinkage, and unreacted alcohol residue affecting air-drying properties. The results above show that only when the molar ratio of unsaturated acid to saturated acid is within the range of this invention can the problem of poor casting fluidity caused by excessive molecular weight be solved, while avoiding the defect of poor toughness caused by excessive hydroxyl groups be avoided. At the same time, the introduction of diethylene glycol further improves the flexibility of the molecular chain, thereby improving the impact resistance of the resin diamond. Only by using the molar ratio of unsaturated acid to saturated acid and the molar ratio of total alcohol to total acid in this invention can the curing speed be improved, achieving a balance between curing efficiency and resin diamond performance.

[0156] In Comparative Example 9, the amount of composite accelerator added was too small, resulting in insufficient free radical initiation efficiency and drying performance, leading to incomplete resin curing, deterioration of mechanical properties, and failure of air-drying properties. In Comparative Example 10, the amount of composite accelerator added was too large, resulting in excessively fast curing rate, uneven molecular chain cross-linking, increased shrinkage, and a tendency for resin diamonds to crack. In Comparative Example 11, the weight ratio of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in the composite accelerator was too low, resulting in uneven resin curing, deterioration of mechanical properties, increased shrinkage, and poorer air-drying properties. In Comparative Example 12, the weight ratio of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in the composite accelerator was too high, resulting in uneven resin curing, increased shrinkage, and a tendency for resin diamonds to crack.

[0157] In step (1) of Comparative Example 13, the addition of all maleic anhydride and diethylene glycol at once resulted in uneven distribution of unsaturated double bonds in the molecular chain, increased defects in the crosslinking network, a significant decrease in mechanical properties, and failure of air-drying properties. The results of Comparative Example 14 show that excessively low temperatures lead to incomplete DCPD reaction, which disrupts the regularity of the resin molecular chain, resulting in deterioration of mechanical and processing properties. The results of Comparative Example 15 show that excessively high temperatures easily induce vigorous self-polymerization, which disrupts the regularity of the resin molecular chain, leading to deterioration of mechanical and processing properties. In step (3) of Comparative Example 16, the composite accelerator was not premixed at 25~60℃ and was directly added to the system, resulting in uneven dispersion of it in the resin. Differences in curing rates caused internal stress, failure of air-drying properties, and a decrease in mechanical properties.

[0158] The casting of this invention has a tensile strength of 40.55~70.46 MPa, a tensile modulus of elasticity of 1869~3890 MPa, an elongation at break of 2.67~7.63%, a flexural strength of 40.74~95.40 MPa, a flexural modulus of elasticity of 1538~3525 MPa, an impact strength of 4.04~7.54 kJ / m², a Barcol hardness of 19~35 HBa, a linear shrinkage rate of 1.24~2.52%, and a solid content of 75.6~79.5%.

[0159] The composite accelerator of this invention is used within a certain range, and the ratio of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate is within the range of 1:2 to 4:6. Only when the composite accelerator is used can it improve the air-drying performance of resin diamonds, so as to achieve rapid demolding and improve the color of the product, and meet the requirements of the transparency of resin diamonds.

[0160] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An unsaturated polyester resin for use with diamond resins, characterized in that, The product, by weight, comprises the following components: 620-680 parts maleic anhydride, 285-540 parts dicyclopentadiene, 124-500 parts diethylene glycol, 60-150 parts ethylene glycol, 0.29-0.45 parts primary antioxidant, 0.29-0.45 parts secondary antioxidant, 0.08-0.22 parts primary polymerization inhibitor, 0.14-0.19 parts secondary polymerization inhibitor, 0.93-1.07 parts paraffin wax, 360-495 parts styrene, 19-23 parts composite accelerator, and 97-103 parts water; the composite accelerator is composed of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in a weight ratio of 1:2 to 4:

6. The method for preparing the unsaturated polyester resin for the resin diamond includes the following steps: (1) Weigh out a portion of maleic anhydride, a portion of diethylene glycol, the first antioxidant and water according to the weight and add them to the reaction vessel. After heating to 110~120℃, add dicyclopentadiene and keep warm for 1~2h. (2) Weigh out the ethylene glycol, the remaining maleic anhydride, the remaining diethylene glycol, the second antioxidant and the first polymerization inhibitor by weight and add them to the reaction vessel of step (1). Heat to 195~198℃ and react until the acid value reaches 25~35mgKOH / g. (3) Cool the product obtained in step (2) to 175~185℃, add the second polymerization inhibitor and paraffin; cool to ≤60℃, add styrene and composite accelerator; mix well to obtain unsaturated polyester resin for resin diamond. The composite accelerator mentioned in step (3) is obtained by premixing cobalt isooctanoate, copper isooctanoate and potassium isooctanoate in a weight ratio of 1:2~4:6 at 25~60℃.

2. The unsaturated polyester resin for diamond resin according to claim 1, characterized in that, The molar ratio of the unsaturated acid to dicyclopentadiene in the unsaturated polyester resin component of the resin diamond is 1.55~3.00:

1.

3. The unsaturated polyester resin for diamonds according to claim 1, characterized in that, The molar ratio of the unsaturated acid to dicyclopentadiene in the unsaturated polyester resin component of the resin diamond is 1.61~2.04:

1.

4. The unsaturated polyester resin for diamonds according to claim 1, characterized in that, The first and second antioxidants are 2,6-di-tert-butyl-4-methylphenol or triphenyl phosphite.

5. The unsaturated polyester resin for diamond resin according to claim 1, characterized in that, The first and second polymerization inhibitors are methylhydroquinone, 4-tert-butylcatechol, or hydroquinone.

6. The unsaturated polyester resin for diamond resin according to claim 1, characterized in that, The composite accelerator is composed of cobalt isooctanoate, copper isooctanoate, and potassium isooctanoate in a weight ratio of 1:2.7 to 3.3:

6.

7. The unsaturated polyester resin for diamond resin according to claim 1, characterized in that, In step (1), the amount of maleic anhydride added accounts for 73.5-83.9% of the total amount of maleic anhydride added, and in step (2), the amount of maleic anhydride added accounts for 16.1-26.5% of the total amount of maleic anhydride added; in step (1), the amount of diethylene glycol added accounts for 11.2-50.0% of the total amount of diethylene glycol added, and in step (2), the amount of diethylene glycol added accounts for 50.0-88.8% of the total amount of diethylene glycol added.