High flexibility novolak modified resin

Abstract

The present application relates to a kind of high flexibility phenol-free rosin modified resin, belong to rosin resin technical field.Its raw material is composed of rosin, maleic anhydride, phthalic anhydride, pentaerythritol, glycerol, acrylic ester monomer and magnesium oxide.The preparation process includes four key reactions: (1) rosin and maleic anhydride are constructed rigid skeleton by Diels-Alder reaction;(2) introduce phthalic anhydride, form dense crosslinking network;(3) pentaerythritol and glycerol complex esterification;(4) by in-situ RAFT polymerization of acrylic ester monomer, interface binding energy is improved.The resin does not contain phenol-formaldehyde component, VOCs emission is less than 50g / L, free formaldehyde is not detected, with high flexibility, heat resistance and excellent chemical resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rosin resin, and relates to a high-flexibility phenol-free rosin modified resin. BACKGROUND

[0002] Rosin is an important natural resin mainly extracted from the resin of Pinaceae plants. Due to its unique chemical structure and excellent physical and chemical properties, rosin has a wide range of applications in industry. Traditionally, rosin has been used to manufacture materials such as coatings, adhesives, inks and rubbers, mainly relying on its acidic components and good adhesion. However, the brittleness and easy oxidation characteristics of rosin limit its wider application. In recent years, researchers have been working to develop modification techniques for rosin to improve its mechanical properties and chemical stability. Modification techniques include esterification, hydrogenation, polymerization and crosslinking, etc. Through chemical reactions, the flexibility, weather resistance and chemical resistance of rosin are improved, so that it can better meet the needs of modern industry.

[0003] Despite the significant progress made in rosin modification techniques, there are still some problems that need to be solved. For example, traditional rosin modification methods usually require the use of phenol or other toxic compounds for reaction, which not only pollutes the environment, but also poses a potential threat to the health of operators. Therefore, developing green and environmentally friendly rosin modification techniques has become the focus of current research. In order to achieve this goal, many researchers have begun to explore phenol-free rosin modification approaches, using natural or low-toxicity compounds as reaction reagents to reduce the impact on the environment.

[0004] In recent years, researchers have attempted to improve the flexibility of rosin resin by acrylate copolymerization or polyol plasticization, but still face challenges: physical blending methods (such as direct addition of acrylate elastomers) are prone to phase separation due to poor interfacial compatibility, resulting in a sharp drop in mechanical properties; chemical grafting methods (such as free radical grafting of acrylate monomers) are limited by the lack of active sites on rosin molecules, resulting in low grafting rates and yellowing of the resin caused by high-temperature initiators; phenol-free alternatives (such as epoxy resin modification) may reduce toxicity, but it is difficult to balance heat resistance and chemical resistance. Therefore, the development of a phenol-free, high-flexibility, process-controllable rosin modified resin has become an urgent need. SUMMARY

[0005] The purpose of the present application is to provide a high-flexibility phenol-free rosin modified resin with the characteristics of phenol-free and high flexibility.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A high-flexibility non-phenolic rosin modified resin, raw materials of which include, by mass fraction, rosin 50-70 parts, maleic anhydride 15-25 parts, phthalic anhydride 5-10 parts, pentaerythritol 10-20 parts, glycerol 5-10 parts, acrylic ester monomer 1-5 parts, and magnesium oxide 0.1-3 parts;

[0008] The high-flexibility non-phenolic rosin modified resin is prepared by the following steps:

[0009] (1) The rosin is heated to 120-140℃ for melting, nitrogen is introduced for protection, magnesium chloride is added as a catalyst, after stirring for 20-40 min, the temperature is raised to 160-180℃, maleic anhydride is added for reaction for 2-3 h, the conjugated double bond in the rosin and the dienophile structure in the maleic anhydride undergo a cycloaddition reaction under the catalysis of the magnesium chloride, and a rigid cyclic structure is introduced;

[0010] (2) The temperature is lowered to 130-150℃, phthalic anhydride is added for reaction for 0.5-1.5 h, and a complex ester is generated, the phthalic anhydride and the hydroxyl or carboxyl in the rosin-maleic acid undergo an esterification reaction to form a crosslinking ester bond;

[0011] (3) Pentaerythritol and glycerol are added in sequence, the temperature is raised to 220-240℃, and the esterification is carried out for 4-5 h to obtain a polyol complex ester, the hydroxyl in the pentaerythritol and glycerol and the carboxyl or anhydride group in the product of step (2) undergo an esterification polycondensation reaction, the pentaerythritol enhances the crosslinking rigidity, and the glycerol introduces a flexible segment to synergistically optimize the mechanical properties;

[0012] (4) After the acrylic ester monomer is uniformly mixed, it is added dropwise into the polyol complex ester and stirred uniformly, 0.1-1% of a RAFT agent and 0.1-0.5% of an initiator based on the mass of the monomer are added, and the reaction is carried out at 60-80℃ for 2-3 h, the initiator decomposes to generate free radicals, the free radicals attack the acrylic ester monomer, and then the acrylic ester monomer is grafted to the rosin ester through the RAFT agent.

[0013] As a preferred technical solution of the present application, the rosin is at least one of gum rosin, wood rosin, or hydrogenated rosin.

[0014] As a preferred technical solution of the present application, the weight ratio of the pentaerythritol to the glycerol is 1.5-2.5:1.

[0015] As a preferred technical solution of the present application, the acrylic ester monomer is butyl acrylate and methyl methacrylate at a mass ratio of 7-8:2-3.

[0016] As a preferred technical solution of the present application, the RAFT agent in step A2 is a dithiobenzoate, and the initiator is azobisisobutyronitrile or benzoyl peroxide.

[0017] Advantages of the present application:

[0018] (1) The present application forms a six-membered ring rigid skeleton by Diels-Alder reaction of maleic anhydride with the conjugated double bond of rosin, replacing the phenolic crosslinking structure, thereby eliminating the generation of formaldehyde and phenol from the source; magnesium oxide is used to replace the traditional acidic catalyst (such as sulfuric acid), avoiding resin yellowing and equipment corrosion; VOCs emission is significantly reduced, and environmental performance is leading.

[0019] (2) The present application generates a rigid skeleton by Diels-Alder reaction, and the conjugated double bond in rosin and maleic anhydride undergoes cycloaddition at 160-180℃ to generate a cyclic ester, thereby improving the heat distortion temperature; phthalic anhydride is esterified at a low temperature of 130-150℃ to form a crosslinked rigid network, thereby significantly enhancing chemical resistance; pentaerythritol (tetrafunctionality) and glycerol (trifunctionality) are compounded and esterified at a ratio of 1.5-2.5:1, the former constructs a high crosslinking rigid region, and the latter introduces flexible branches, thereby achieving a balance between strength and flexibility.

[0020] (3) In view of the poor compatibility of the traditional blending method, the present application uses dithiobenzoate as an initiator to make the polymerization reaction relatively mild, thereby generating rosin-g-(BA-b-MMA) block copolymer to improve the interfacial binding energy; the butyl acrylate flexible segment is anchored to the rosin rigid skeleton through π-π conjugation, thereby giving the resin super flexibility, while the methyl methacrylate hard segment maintains heat resistance; the dense crosslinking network and the acrylic ester hydrophobic chain synergistically improve the chemical solvent resistance. DETAILED DESCRIPTION

[0021] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined purposes, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

[0022] Example 1

[0023] A high-flexibility phenolic-free rosin modified resin, comprising the following raw material components by weight: rosin 60 parts, maleic anhydride 20 parts, phthalic anhydride 7 parts, pentaerythritol 15 parts, glycerol 8 parts, acrylic ester monomer 3 parts, and magnesium oxide 1.5 parts;

[0024] The resin is prepared by the following steps:

[0025] (1) The rosin is heated to 130℃ to melt, nitrogen is introduced for protection, magnesium chloride is added as a catalyst, and after stirring for 30 min, the temperature is raised to 170℃, maleic anhydride is added and reacted for 2.5 h to obtain rosin-maleic acid;

[0026] (2) cooling to 140℃, adding phthalic anhydride to react for 1h to form a complex ester;

[0027] (3) adding pentaerythritol and glycerol in sequence, heating to 230℃, and esterifying for 4.5h to obtain a polyol complex ester;

[0028] (4) mixing acrylic ester monomers uniformly, then adding them dropwise into the polyol complex ester, stirring uniformly, adding 0.5% of the mass of the monomers of a RAFT agent and 0.3% of the mass of the monomers of an initiator, and reacting at 70℃ for 2.5h;

[0029] (5) stopping the reaction by passing in air and cooling to room temperature.

[0030] The rosin is a mixture of gum rosin and wood rosin in a mass ratio of 1:1.

[0031] The acrylic ester monomers are butyl acrylate and methyl methacrylate in a mass ratio of 7.5:2.4.

[0032] The RAFT agent in step A2 is 2-[dodecylsulfanyl(thiocarbonyl)thio]-2-methylpropanoic acid; and the initiator is azobisisobutyronitrile.

[0033] Example 2

[0034] A high-flexibility non-phenolic rosin modified resin, comprising the following raw material components in parts by weight: rosin 50 parts, maleic anhydride 15 parts, phthalic anhydride 5 parts, pentaerythritol 10 parts, glycerol 5 parts, acrylic ester monomers 1 part, and magnesium oxide 0.1 part;

[0035] The resin is prepared by the following steps:

[0036] (1) heating rosin to 120℃ to melt, passing in nitrogen to protect, adding magnesium chloride as a catalyst, stirring for 20min, then heating to 160℃, and adding maleic anhydride to react for 2h to obtain rosin-maleic acid;

[0037] (2) cooling to 130℃, adding phthalic anhydride to react for 0.5h to form a complex ester;

[0038] (3) adding pentaerythritol and glycerol in sequence, heating to 220℃, and esterifying for 4h to obtain a polyol complex ester;

[0039] (4) mixing acrylic ester monomers uniformly, then adding them dropwise into the polyol complex ester, stirring uniformly, adding 0.1% of the mass of the monomers of a RAFT agent and 0.1% of the mass of the monomers of an initiator, and reacting at 60℃ for 2h;

[0040] (5) stopping the reaction by passing in air and cooling to room temperature.

[0041] The rosin is wood rosin and hydrogenated rosin at a mass ratio of 1:1.

[0042] The acrylate monomer is butyl acrylate and methyl methacrylate at a mass ratio of 7:2.

[0043] The RAFT agent in step A2 is dithiobenzoic acid 1-cyano-1-methyl-4-oxo-4-(2- thioxothiazolidin-3-yl)butyl ester; and the initiator is azobisisobutyronitrile.

[0044] Example 3

[0045] A high-flexibility non-phenolic rosin modified resin, comprising the following raw material components by weight: rosin 70 parts, maleic anhydride 25 parts, phthalic anhydride 10 parts, pentaerythritol 20 parts, glycerol 10 parts, acrylate monomer 5 parts, and magnesium oxide 3 parts;

[0046] The resin is prepared by the following steps:

[0047] (1) The rosin is heated to 140°C to melt, nitrogen is introduced for protection, magnesium chloride is added as a catalyst, after stirring for 40 min, the temperature is raised to 180°C, maleic anhydride is added and reacted for 3h to obtain rosin-maleic acid;

[0048] (2) The temperature is lowered to 150°C, phthalic anhydride is added and reacted for 1.5h to form a complex ester;

[0049] (3) Pentaerythritol and glycerol are added in sequence, the temperature is raised to 240°C, and esterification is carried out for 5h to obtain a polyol complex ester;

[0050] (4) The acrylate monomer is mixed uniformly, then added dropwise into the polyol complex ester and stirred uniformly, 1% of the monomer mass of RAFT agent and 0.5% of the monomer mass of initiator are added, and the reaction is carried out at 80°C for 3h;

[0051] (5) Air is introduced to terminate the reaction, and the temperature is cooled to room temperature.

[0052] The rosin is wood rosin and hydrogenated rosin at a mass ratio of 1:1.

[0053] The acrylate monomer is butyl acrylate and methyl methacrylate at a mass ratio of 8:3.

[0054] The RAFT agent in step A2 is 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropanoic acid; and the initiator is benzoyl peroxide.

[0055] Example 4

[0056] A high-flexibility phenol-free rosin modified resin, comprising the following raw material components by weight: rosin 55 parts, maleic anhydride 22 parts, phthalic anhydride 8 parts, pentaerythritol 12 parts, glycerol 7 parts, acrylic ester monomer 2 parts and magnesium oxide 2 parts;

[0057] The resin is prepared by the following steps:

[0058] (1) The rosin is heated to melt at 125°C, nitrogen is introduced for protection, magnesium chloride is added as a catalyst, after stirring for 25 min, the temperature is raised to 175°C, maleic anhydride is added and reacted for 2h to obtain rosin-maleic acid;

[0059] (2) The temperature is lowered to 145°C, phthalic anhydride is added and reacted for 1h to generate a complex ester;

[0060] (3) Pentaerythritol and glycerol are added in sequence, the temperature is raised to 225°C, and esterification is carried out for 4h to obtain a polyol complex ester;

[0061] (4) After the acrylic ester monomer is uniformly mixed, it is added dropwise into the polyol complex ester and stirred uniformly, 0.3% of the mass of the monomer of a RAFT reagent and 0.5% of the mass of the monomer of an initiator are added, and reaction is carried out at 65°C for 3h;

[0062] (5) Air is introduced to terminate the reaction, and the temperature is lowered to room temperature.

[0063] The rosin is DE gum rosin, wood rosin and hydrogenated rosin in a mass ratio of 1:1:1.

[0064] The acrylic ester monomer is butyl acrylate and methyl methacrylate in a mass ratio of 7:3.

[0065] The RAFT reagent in step A2 is dithiobenzoic acid 1-cyano-1-methyl-4-oxo-4-(2-thioxothiazolidin-3-yl) butyl ester; and the initiator is benzoyl peroxide.

[0066] Comparative Example 1

[0067] On the basis of Example 1, phthalic anhydride is not added in the components, the addition amount of maleic anhydride is increased to 28 parts by weight, and the rest is consistent with Example 1.

[0068] Comparative Example 2

[0069] On the basis of Example 1, maleic anhydride is not added in the components, the addition amount of phthalic anhydride is increased to 28 parts by weight, and the rest is consistent with Example 1.

[0070] Comparative Example 3

[0071] On the basis of Example 1, the reaction temperature of adding maleic anhydride in step (1) is changed to 140℃, and maleic anhydride is reacted with phthalic anhydride at the same temperature, and the rest is the same as Example 1.

[0072] Comparative Example 4

[0073] On the basis of Example 1, the reaction temperature of adding phthalic anhydride in step (2) is changed to 170℃, and phthalic anhydride is reacted with maleic anhydride at the same temperature, and the rest is the same as Example 1.

[0074] Comparative Example 5

[0075] On the basis of Example 1, the addition amount of pentaerythritol in the raw material component is changed to 12 parts by weight, and the addition amount of glycerol is changed to 11 parts by weight, and the rest is the same as Example 1.

[0076] Comparative Example 6

[0077] On the basis of Example 1, the addition amount of pentaerythritol in the raw material component is changed to 17 parts by weight, and the addition amount of glycerol is changed to 6 parts by weight, and the rest is the same as Example 1.

[0078] Comparative Example 7

[0079] On the basis of Example 1, step (4) directly adds an acrylic elastomer, and the rest is the same as Example 1; the preparation method of the acrylic elastomer is to mix butyl acrylate and methyl methacrylate at a ratio of 7.5:2.4, stir in toluene until completely dissolved; add 0.5% initiator benzoyl peroxide based on the mass of acrylic ester, remove oxygen by nitrogen, and heat to 80℃; react at 80℃ for 6 hours, add 0.1% hydroquinone to terminate the reaction, cool and pour into ethanol to precipitate, filter and vacuum dry for 24 hours (60℃), to obtain white elastomer particles, acrylic elastomer.

[0080] Comparative Example 8

[0081] On the basis of Example 1, the addition amount of rosin in the raw material is reduced to 40 parts by weight, and 20 parts by weight of phenolic resin is added, and the rest is the same as Example 1.

[0082] Performance test:

[0083] Tensile strength and elongation at break: refer to GB / T 1040.3-2006, pour into a mold to form a sheet and test on a CMT5104 type microcomputer controlled electronic universal testing machine, and the tensile strength and elongation at break are measured. The experimental temperature is 25℃, the relative humidity is 40%, the sample gauge length is 25mm, the sample width is 6mm, and the tensile rate is 5mm / min;

[0084] Softening point: the determination method refers to GB / T 8146-2003 "Rosin Test Methods";

[0085] Peeling strength: the sample is prepared according to GB / T 2790-1995 standard, and the 180° peeling strength is measured by using a universal tensile testing machine;

[0086] Volatile organic compounds (VOC): tested according to GB / T 39600-2021 standard;

[0087] Hardness: tested according to GB / T 6739-2022 "Pencil Method for Determining Film Hardness of Pigment and Varnish"; the test results are shown in Table 1:

[0088] Table 1

[0089]

[0090]

[0091] Acid and alkali resistance and solvent resistance: according to GB 9274-1988 method, method A (immersion method) is selected: 2 / 3 of each group of three test panels are immersed in 10% by mass sulfuric acid aqueous solution, 10% by mass NaOH aqueous solution and dimethylbenzene at room temperature for 14 days, and the changes of the coating (such as loss of gloss, whitening, bubbling, peeling, etc.) are observed and recorded;

[0092] The test results are shown in Table 2:

[0093] Table 2

[0094] acid resistance alkali resistance solvent resistance Example 1 no change no change no change Example 2 no change slight discoloration no change Example 3 no change no change no change Example 4 no change no change no change Comparative Example 1 surface whitening peeling (area 10%) swelling rate 8% Comparative Example 2 bubbles (diameter 1-2 mm) whitening, discoloration swelling rate 6% Comparative Example 3 edge peeling peeling (area 15%) swelling rate 12% Comparative Example 4 surface cracking peeling (area 20%) swelling rate 15% Comparative Example 5 slight discoloration whitening swelling rate 5% Comparative Example 6 no change no change swelling rate 2% Comparative Example 7 surface wrinkling peeling (area 25%) swelling rate 18% Comparative Example 8 no change no change edge slight swelling

[0095] From the test results in Table 1, it can be seen that the VOC content of the examples is significantly lower than that of the phenolic resin-containing comparative example 8, and the elongation at break of comparative example 8 (20% phenolic resin is added) is only 5.0%, which indicates that although the phenolic resin improves the hardness (3H), it seriously deteriorates the flexibility.

[0096] Comparative example 1 (without phthalic anhydride) and comparative example 2 (without maleic anhydride): the crosslinking network is incomplete, the softening point is reduced to 110℃ and 104℃, the tensile strength of comparative example 1 is significantly decreased, and the chemical resistance is significantly decreased.

[0097] Comparative examples 3 and 4 (gradient esterification destruction): isothermal reaction leads to anhydride self-polymerization, and the softening points are reduced to 101℃ and 96℃, respectively, which proves the necessity of gradient temperature (ΔT = 20-40℃) for ordered crosslinking;

[0098] Comparative Example 5 (pentaerythritol / glycerol weight ratio of 1.1:1) and Comparative Example 6 (pentaerythritol / glycerol weight ratio of 2.8:1): the pentaerythritol / glycerol ratio not only balances the strength and flexibility, but also has an impact on the peel strength, the glass strength of Comparative Example 5 decreases significantly;

[0099] Comparative Example 7 (directly physically blending with an acrylate elastomer), the hardness is only B grade, and the interface defect causes the hardness to decrease significantly.

[0100] From the test results in Table 2, the sulfuric acid resistance: the rigid benzene ring structure of phthalic anhydride effectively shields acid erosion (no change in the example); the NaOH resistance: the gradient esterification forms a dense crosslinked network; the xylene resistance: the RAFT compatibilized nanodispersed phase blocks solvent penetration.

[0101] Comparative Example 1 and Comparative Example 2 (anhydride system): Comparative Example 1 (without phthalic anhydride) falls off by 10% in NaOH, proving the key role of phthalic anhydride in alkali resistance; Comparative Example 2 (without maleic anhydride) produces bubbles in sulfuric acid due to the lack of Diels-Alder rigid skeleton;

[0102] Comparative Example 3 and Comparative Example 4 (isothermal reaction): Comparative Example 3 (140°C isothermal) falls off by 20% in NaOH due to uneven crosslinking caused by anhydride self-polymerization; Comparative Example 4 (170°C isothermal) is brittle due to excessive crosslinking, with a xylene swelling rate of 15%;

[0103] Comparative Example 5 (pentaerythritol / glycerol = 1.1:1): too many flexible segments result in a decrease in crosslinking density, with a xylene swelling rate of 5%; Comparative Example 6 (pentaerythritol / glycerol = 2.8:1): high rigidity design results in lower chemical resistance, but the elongation at break decreases to 20.3%;

[0104] Comparative Example 7 (physical blending): phase separation results in an increase in solvent penetration channels, with a xylene swelling rate of 18%; poor interface bonding, with a NaOH immersion fall-off of 30%;

[0105] Comparative Example 8: although phenolic resin improves chemical resistance, it has poor environmental friendliness and extremely low flexibility.

[0106] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any indirect modification, equivalent change and modification of the above embodiments based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A highly flexible, phenol- and rosin-free modified resin, characterized in that: By weight, its raw materials contain the following components: 50-70 parts rosin, 15-25 parts maleic anhydride, 5-10 parts phthalic anhydride, 10-20 parts pentaerythritol, 5-10 parts glycerol, 1-5 parts acrylate monomer and 0.1-3 parts magnesium oxide. The highly flexible, phenol-free rosin-modified resin is prepared through the following steps: (1) Rosin and maleic anhydride undergo Diels-Alder addition under magnesium oxide catalysis to obtain rosin-maleic acid; (2) Add phthalic anhydride to the rosin-maleic acid obtained in step (1) to carry out esterification reaction; (3) Add pentaerythritol and glycerol sequentially to the esterification product obtained in step (2) to carry out polyol complex esterification; (4) The polyol composite esterification product obtained in step (3) is subjected to carbon-carbon double bond polymerization reaction with acrylate monomer to obtain a highly flexible phenol-free rosin modified resin. The weight ratio of pentaerythritol to glycerol is 1.5-2.5:1; The addition in step (1) is carried out under nitrogen protection at a reaction temperature of 160-180℃; The esterification reaction temperature in step (2) is 130-150℃; In step (4), the polymerization reaction is carried out by adding RAFT reagent and initiator.

2. The high-flexibility phenol-free rosin-modified resin according to claim 1, characterized in that: The rosin is at least one of resin rosin, wood rosin, or hydrogenated rosin.

3. The high-flexibility phenol-free rosin-modified resin according to claim 1, characterized in that: The acrylate monomers are butyl acrylate and methyl methacrylate in a mass ratio of 7-8:2-3.

4. The high-flexibility phenol-free rosin-modified resin according to claim 1, characterized in that: The addition process described in step (1) takes 2-3 hours.

5. The high-flexibility phenol-free rosin-modified resin according to claim 1, characterized in that: The esterification reaction described in step (2) takes 0.5-1.5 hours.

6. The high-flexibility phenol-free rosin-modified resin according to claim 1, characterized in that: The polyol composite esterification reaction in step (3) is carried out at a temperature of 220-240℃ and a reaction time of 4-5h.

7. The high-flexibility phenol-free rosin-modified resin according to claim 1, characterized in that: The polymerization reaction described in step (4) includes the following steps: A1. Under a nitrogen atmosphere, the acrylate monomer is added dropwise to the polyol composite esterification product obtained in step (3); A2. Add 0.1-1% of the monomer mass of RAFT reagent and stir evenly, then add 0.1-0.5% of the monomer mass of initiator to carry out the polymerization reaction.

8. The high-flexibility phenol-free rosin-modified resin according to claim 7, characterized in that: The RAFT reagent in step A2 is a dithiobenzoate; the initiator is azobisisobutyronitrile or benzoyl peroxide.

9. The high-flexibility phenol-free rosin-modified resin according to claim 7, characterized in that: The polymerization reaction in step A2 is carried out at a temperature of 60-80℃ for 2-3 hours.

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