CN116120535A - Modified unsaturated polyester and preparation method thereof - Google Patents

Abstract

Relates to the technical field of unsaturated polyester resin, in particular to modified unsaturated polyester and a preparation method thereof. Terephthalic acid needs strong acid as a catalyst at high temperature to react with dihydric alcohol to prepare polyester, and the generated polyester has poor compatibility with styrene and is easy to laminate, so that the production and application of the terephthalic type unsaturated resin are greatly limited. The invention comprises the following raw materials in percentage by weight: PET, diethylene glycol, benzoic acid, phthalic anhydride, ethylene glycol, maleic anhydride, dicyclopentadiene, a catalyst, an antioxidant and a polymerization inhibitor, and the balance of water; the mol number of dicyclopentadiene accounts for 14.5-33% of the total mol number of alcohol in the raw material; the mole number of PET accounts for 34-35% of the total mole number of alcohol in the raw material. The reaction difficulty is reduced by utilizing PET and dicyclopentadiene, the problem of poor compatibility of the para-benzene type unsaturated polyester and styrene is solved, and the problem that the pure dicyclopentadiene modified resin is not ageing-resistant is solved.

Description

A kind of modified unsaturated polyester and preparation method thereof

technical field

It relates to the technical field of unsaturated polyester resin, in particular to a modified unsaturated polyester and a preparation method thereof.

Background technique

The two carboxyl groups of terephthalic acid are in the para position of the benzene ring, with small interaction and stable chemical properties; the unsaturated resin produced by the reaction of terephthalic acid has good molecular symmetry, neat structure and good mechanical properties And excellent corrosion resistance, heat resistance. However, its reactivity is low and the reaction conditions are high. It needs a strong acid under high temperature as a catalyst to react with diols. The resulting polyester has poor compatibility with styrene and is easy to delaminate, which greatly limits the use of benzene-type unsaturated resins. production and application.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a modified unsaturated resin with good compatibility with styrene, aging resistance, low reaction difficulty and small environmental burden and its preparation method.

The technical solution adopted by the present invention to solve the technical problem is: a modified unsaturated polyester, characterized in that: the raw materials include: PET25~31%, diethylene glycol 23~29%, benzoic acid 2~4% by weight %, phthalic anhydride 3~8%, ethylene glycol 1~3%, maleic anhydride 20~25%, dicyclopentadiene 9~16%, catalyst 0.05~0.06%, antioxidant 0.05~ 0.07% and polymerization inhibitor 0.001 ~ 0.002%, and the balance is water; Wherein, the molar number of described dicyclopentadiene accounts for 14.5 ~ 33% of the total molar number of alcohol in the raw material; 34~35% of the total moles of alcohol.

The two carboxyl groups of terephthalic acid are in the para position of the benzene ring, the molecular structure is symmetrical, and the dipole moment is equal to zero. The polyester produced with it has a high tendency to crystallize, has poor compatibility with styrene, and is easy to delaminate, which affects its use. The addition of dicyclopentadiene destroys the symmetry of the molecular structure of polyester and reduces the crystallization ability of polyester; on the other hand, according to the principle of similar compatibility, the structure of dicyclopentadiene is similar to that of styrene. All aspects are conducive to the compatibility of benzene-type polyester and styrene. The dicyclopentadiene molar number is lower than 14.5%, unsaturated polyester and styrene are poorly compatible, and the effect of dicyclopentadiene in this reaction system is not reflected; Diene is decomposed into cyclopentadiene, and cyclopentadiene reacts with the unsaturated double chain in the polyester molecular chain. As a result, the unsaturated double bond of the polyester is reduced, the activity is reduced, and the curing speed is slowed down. The gel time is too long, which is not conducive to the use of resin. If the ratio of dicyclopentadiene to PET is within the corresponding range, the unsaturated polyester molecules produced by the reaction will not be ineffective due to too little dicyclopentadiene segment, and will not lose the para-benzene segment due to too much dilution. The original excellent performance of benzene resin.

Preferably, the moles of dicyclopentadiene account for 29-54% of the total moles of maleic anhydride in the raw material.

Reaction increases the proportion of maleic anhydride to be beneficial to the process of this synthetic reaction, improves the yield and the purity of product, but the proportion of maleic anhydride is too large to produce by-product dicyclopentadiene maleic acid diester; If the proportion is too low, dicyclopentadiene will be decomposed into cyclopentadiene as a by-product. Both by-products will deepen the color of the final product and affect the color of the final product unsaturated resin. With the molar ratio within this range, the two by-products are less and the final cured unsaturated polyester has excellent strength.

Preferably, the catalyst is a mixture of dibutyltin oxide and zinc acetate in a weight ratio of 1:4.

Among many metal ions, zinc ion has the best catalytic effect. As a metal salt, zinc acetate has high catalytic activity and can be dissolved in a solvent at a higher temperature to fully contact the reactant to accelerate the alcoholysis reaction process; Compared with other single metal oxides, tin-based tin oxide has more acid sites and the interaction between zinc and tin ions, which has better catalytic effect. However, as a Lewis acid, zinc acetate is corrosive, and choosing this ratio to compound the catalyst can reduce the corrosion of the reactor and reduce the production cost under the premise of ensuring the catalytic effect.

Preferably, the polymerization inhibitor is a mixture of hydroquinone and naphthenic acid ketone in a weight ratio of 2:1.

Hydroquinone is added in the alcoholysis and polycondensation reaction to slow down the reaction speed in the early stage and prevent the occurrence of sudden polymerization in the polycondensation reaction. A single inhibitor is selected for the first polymerization inhibition, which is convenient for the gelation time of the final product in actual production. Adjustment; the choice of naphthenic acid ketone is to ensure the storage stability of the product in the later stage.

Preferably, the antioxidant is a mixture of 2,6-p-tert-butylxylenol and triphenyl phosphite in a weight ratio of 1:1.

Preferably, the number of moles of PET accounts for 60% of the total number of moles of diethylene glycol in the raw material.

When the amount of diethylene glycol is low, the alcoholysis efficiency is low. As the amount of diethylene glycol increases, more diethylene glycol molecules will penetrate into the interior of the PET material, causing more PET molecules to swell and decompose. , the corresponding degree of alcoholysis will increase. However, with the increase of the amount of diethylene glycol, the alcoholysis efficiency of PET will decrease instead. The reason is that after the amount of alcohol is too much, the effect of swelling PET is limited. At this time, it will no longer have a great impact on the degradation of PET. , but the use of too much diethylene glycol will also reduce the relative concentration of PET. Therefore, under the premise of considering the saving of raw materials, and taking into account the alcoholysis efficiency, this ratio is the most suitable.

A kind of preparation method of above-mentioned modified unsaturated polyester, it is characterized in that: comprise the following steps:

1) PET, diethylene glycol, benzoic acid, phthalic anhydride, ethylene glycol, catalyst and antioxidant are mixed and heated to 200~220°C, and stirred until the acid value is lower than 5mgKOH/g;

2) Mix water, dicyclopentadiene and antioxidant and raise the temperature to 120℃, add maleic anhydride dropwise, then raise the temperature to 125~130℃ and keep it for 2~3h;

3) Mix the mixture obtained in step 1) and step 2), add a polymerization inhibitor, raise the temperature to 150~170°C and keep it for 0.5~1.5h; continue to raise the temperature to 200~220°C and keep it until the acid value is 14~20mgKOH/g;

4) Cool down to 120~180°C and add polymerization inhibitor and styrene to obtain modified unsaturated polyester;

Wherein, the antioxidant described in step 1) is 50-70% of the total amount of antioxidant in the raw material, and the antioxidant in step 2) is the rest of the antioxidant in the raw material; the polymerization inhibitor in step 3) is 20-30% of the total amount of the polymerization inhibitor in the raw material, and the polymerization inhibitor in step 4) is the rest of the polymerization inhibitor in the raw material.

Preferably, the temperature reduction in step 4) is as follows: firstly lower the temperature to below 180°C, add a polymerization inhibitor, then lower the temperature to 120-130°C and add styrene.

Compared with the prior art, the present invention has the beneficial effects as follows: 1. The addition of terephthalic acid is replaced by PET modification, which reduces the difficulty of the reaction and avoids the introduction of the necessary concentrated sulfuric acid catalyst for the terephthalic acid reaction, and PET can be recycled, which has little burden on the environment. 2. Through the modification of dicyclopentadiene, the problem of poor compatibility between p-benzene-type unsaturated polyester and styrene is solved, and the physical properties of the resin are further improved, but too many double rings will lead to low viscosity and gelation of the system With prolonged time, the strength of the final unsaturated polyester may decrease. 3. Through the benzene modification of PET, the problem of aging resistance of pure dicyclopentadiene modified resin is solved.

Detailed ways

The present invention will be further described below in conjunction with embodiment, and embodiment 1 is the best embodiment of the present invention.

A kind of preparation method of modified unsaturated polyester, adopts following steps:

1) PET, diethylene glycol, benzoic acid, phthalic anhydride, ethylene glycol, catalyst and antioxidant are mixed and heated to 200~220°C, and stirred until the acid value is lower than 5mgKOH/g;

2) Mix water, dicyclopentadiene and antioxidant, heat up to 120°C, start adding maleic anhydride dropwise for 2 hours, then raise the temperature to 125~130°C for 2.5 hours, then cool down;

3) Add a polymerization inhibitor, raise the temperature to 150~170°C and keep it warm for 1 hour; continue to raise the temperature and control the temperature at 200~220°C to keep it warm until the acid value is 14~20mgKOH/g (sampling and monitoring will start after reaching the temperature for 0.5h);

4) Cool down to 180°C and add a polymerization inhibitor, continue to cool down to 130°C and add styrene (the temperature of the adding process is controlled at 120~130°C, to avoid the influence of low temperature on styrene mixing) to obtain modified unsaturated polyester;

Wherein, the antioxidant described in step 1) is 50-70% of the total amount of antioxidant in the raw material, and the antioxidant in step 2) is the rest of the antioxidant in the raw material; the polymerization inhibitor in step 3) is 25% of the total amount of the polymerization inhibitor in the raw material, and the polymerization inhibitor in step 3) is all the rest of the polymerization inhibitor in the raw material.

Embodiment 1~8

A modified unsaturated polyester, the ratio of raw materials in Examples 1 to 8 refers to the following Table 1, and the unit of the amount of each raw material in Table 1 is g.

Table 1 Example raw material table

.

The above-mentioned catalyst is a mixture of dibutyltin oxide and zinc acetate in a weight ratio of 1:4; the antioxidant is 2,6-p-tert-butylxylenol; the polymerization inhibitor is hydroquinone and copper naphthenate 2:1 mixture by weight, the polymerization inhibitor in step 3) is 50% of the total amount of hydroquinone, and the amount of polymerization inhibitor in step 4) is all remaining hydroquinone and all naphthenic acid ketones .

Comparative example 1~5

A modified unsaturated polyester, the raw material ratio of comparative examples 1-5 refers to the following table 2.

Table 2 comparative example raw material list

.

Wherein, no PET was added in Comparative Example 1; a small amount of over-range dicyclopentadiene was added in Comparative Example 2; excessive dicyclopentadiene was added in Comparative Example 3; dicyclopentadiene was not added in Comparative Example 4; Comparative Example 5 Add a small amount of dicyclopentadiene.

Performance Testing

1. Appearance

After standing the prepared unsaturated polyester resin to observe whether it is delaminated, it is stored at low temperature to observe whether it is delaminated and fluorescent.

2. Anti-aging

The prepared unsaturated polyester resin was made into a color plate required for the aging resistance test, put into an ultraviolet accelerated weathering tester, and a comparative aging test was carried out, and the test results were taken for 200 hours as a comparison. The amount of change is represented by △E, and the smaller the amount of change, the stronger the aging resistance.

3. Gel time

According to the standard GB7193-2008 requirements of the prepared unsaturated polyester resin, the gel time at 25°C was measured.

4. Bending strength

The prepared unsaturated polyester resin was measured for flexural strength according to the requirements of the standard GB/T2567-2021.

Embodiment and comparative example test result are shown in the following table 3:

Table 3 performance test results

.

In comparative example 1, p-benzene molecular segments are not added, and its aging resistance and bending strength are poor compared with the examples; comparative example 2 exceeds the scope of the examples, and too much dicyclopentadiene is decomposed into by-product cyclopentadiene during the reaction process Diene, which makes the color of the resin darker; excess cyclopentadiene is added to the unsaturated double bond as a monofunctional small molecule, which makes the gelation time of the resin longer; comparative example 3 The molar ratio of dicyclopentadiene to alcohol With dicyclopentadiene and maleic anhydride mol ratio exceeds embodiment range a lot, a large amount of excess dicyclopentadiene decomposes a large amount of cyclopentadiene by-products in the reaction process, and unsaturated bis bond reaction and consume a large amount of initiator free radicals, so that the resin has no tendency to gel, the curing degree of the cured product is insufficient, and the bending performance is greatly reduced; no dicyclopentadiene is added in Comparative Example 4, as a pure p-phenylene resin, and benzene Ethylene has poor compatibility, and the shortcomings of static stratification appear; in comparative example 5, the addition of dicyclopentadiene lower than the range of the examples, first of all, the low addition of dicyclopentadiene cannot effectively destroy the structure of p-phenylene polyester molecules The symmetry and crystallization ability, the compatibility of polyester and styrene have not been effectively improved, and the phenomenon of poor compatibility still occurs at low temperature, and its bending strength is also far behind that of the examples.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention to other forms. Any skilled person who is familiar with this profession may use the technical content disclosed above to change or modify the equivalent of equivalent changes. Example. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (7)

1. A modified unsaturated polyester characterized in that: the raw materials comprise the following components in percentage by weight: 25-31% of PET, 23-29% of diethylene glycol, 2-4% of benzoic acid, 3-8% of phthalic anhydride, 1-3% of ethylene glycol, 20-25% of maleic anhydride, 9-16% of dicyclopentadiene, 0.05-0.06% of a catalyst, 0.05-0.07% of an antioxidant, 0.001-0.002% of a polymerization inhibitor and the balance of water; wherein the mol number of dicyclopentadiene accounts for 14.5-33% of the total mol number of alcohol in the raw material; the mole number of PET accounts for 34-35% of the total mole number of alcohol in the raw material.

2. The modified unsaturated polyester of claim 1, characterized in that: the mole number of dicyclopentadiene accounts for 29-54% of the total mole number of maleic anhydride in the raw material.

3. The modified unsaturated polyester of claim 1, characterized in that: the catalyst is dibutyl tin oxide and zinc acetate according to the weight ratio of 1: 4.

4. The modified unsaturated polyester of claim 1, characterized in that: the polymerization inhibitor is prepared from hydroquinone and ketone naphthenate according to a weight ratio of 2: 1.

5. The modified unsaturated polyester of claim 1, characterized in that: the antioxidant is a mixture of 2, 6-p-tert-butylxylenol and triphenyl phosphite according to a weight ratio of 1:1.

6. The modified unsaturated polyester of claim 1, characterized in that: the mole number of the PET accounts for 60% of the total mole number of the diethylene glycol in the raw material.

7. A process for producing the modified unsaturated polyester according to any one of claims 1 to 6, characterized in that: the method comprises the following steps:

1) Mixing PET, diethylene glycol, benzoic acid, phthalic anhydride, ethylene glycol, a catalyst and an antioxidant, heating to 200-220 ℃, and stirring until the acid value is lower than 5mgKOH/g;

2) Mixing water, dicyclopentadiene and an antioxidant, heating to 120 ℃, dropwise adding maleic anhydride, heating to 125-130 ℃, and preserving heat for 2-3 hours;

3) Mixing the mixture obtained in the step 1) and the step 2), adding a polymerization inhibitor, heating to 150-170 ℃ and preserving heat for 0.5-1.5 h; continuously heating to 200-220 ℃, and preserving heat until the acid value is 14-20 mgKOH/g;

4) Cooling to 120-180 ℃, and adding a polymerization inhibitor and styrene to obtain modified unsaturated polyester;

wherein, the antioxidant in the step 1) is 50-70% of the total amount of the antioxidants in the raw materials, and the antioxidant in the step 2) is the rest of the antioxidants in the raw materials; the polymerization inhibitor in the step 3) is 20-30% of the total amount of the polymerization inhibitor in the raw materials, and the polymerization inhibitor in the step 4) is the total amount of the polymerization inhibitor in the raw materials.