CN109734699B

CN109734699B - Polymerizable II-type photoinitiator and preparation method thereof

Info

Publication number: CN109734699B
Application number: CN201811625950.8A
Authority: CN
Inventors: 刘新月; 姚娜; 董月国; 武瑞; 张齐
Original assignee: Tianjin Jiuri New Materials Co ltd
Current assignee: Tianjin Jiuri New Materials Co ltd
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2021-01-15
Anticipated expiration: 2038-12-28
Also published as: CN109734699A

Abstract

The invention discloses a polymerizable photoinitiator shown as the following formula and a preparation method thereof, wherein the photoinitiator not only improves the compatibility with a photopolymerization system and greatly reduces the residue of the initiator in the photocuring process, but also can be used as a monomer for synthesizing a macromolecular photoinitiator, so that the polymerizable photoinitiator has wide application prospect in the photocuring field.

Description

Polymerizable II-type photoinitiator and preparation method thereof

The technical field is as follows:

the invention relates to a novel polymerizable II-type photoinitiator and a preparation method thereof.

Background art:

the ultraviolet light curing technology is an environment-friendly green technology in the fields of coatings, printing ink, adhesives and the like, and compared with the traditional solvent-containing system, the ultraviolet light curing technology has the outstanding characteristics of no solvent discharge, high efficiency, energy conservation and the like. The main body of the material generally consists of oligomer, monomer and photoinitiator, and is completely cured under the action of enough ultraviolet light, some unexpected problems appear along with the wider application of UV light curing materials, free radicals generated by the initiator have no initiation activity or low initiation activity, the free radicals are remained in a curing film after quenching, and the toxicity generated by the migration and the precipitation of the residual initiator to the surface becomes a potential great hidden danger in the use process.

For food packaging, an important concern is the migration and extraction of compounds that solidify the layers and packaging material. Migration is the process by which compounds are delivered directly between the cured layer and the packaging substrate, and this migration may cause deterioration of the physical properties of the packaging material, but more importantly the compounds may also migrate further into the food product, many of which are themselves less or not toxic, but become toxic when used in large quantities. In view of health hazards, minimizing the amount of migratory and extractable substances is a very important issue in food packaging.

In order to comply with stricter legislative and health requirements which may be set in the future, photoinitiators are required to have very low mobilities and solvent extractions, and photoinitiators are required to have a strictly defined concentration of volatile harmful organic compounds which are released by themselves during the photocuring process. To further reduce their mobility and volatility, in addition to increasing the molecular weight of the initiator in order to reduce the diffusion rate, for example polyfunctional initiators, polymerization initiators; there is also a method of increasing the reactivity thereof so as to build a polymerization network, such as a polymerizable initiator, which is a part of a polymer film formed by polymerization of the initiator itself under irradiation of UV light, containing both a photoactive group and an unsaturated group in the molecule, and which has a small molecule residue, good compatibility with a resin, and no migration.

The invention content is as follows:

the invention aims to provide a polymerizable photoinitiator and a preparation method thereof, and the polymerizable photoinitiator and the preparation method thereof have the following advantages: 1) the prepared polymerizable photoinitiator has high initiating activity, 2) good compatibility with resin, and 3) small mobility.

The invention provides a polymerizable photoinitiator, which has a structural formula (I):

wherein: r is selected from H, C1-C4 alkyl.

Formula I preferably has the following structure:

the invention provides a preparation method of a compound of formula (I), which can be carried out by the following reaction equation:

wherein: r is selected from H, C1-C4 alkyl.

The preparation method of the compound of formula (I) provided by the invention comprises the following steps:

1) pentaerythritol diacrylate reacts with alkyl substituted chloroacetyl chloride (IV) under alkaline conditions to generate a compound shown in a formula (II);

2) the compound of the formula (II) obtained in the step 1) is reacted with corresponding 4-thioxanthone formic acid under the action of a catalyst and a polymerization inhibitor to obtain the compound of the formula (I).

The invention provides a preparation method of a compound shown in a formula (I), which is characterized in that in the step 1), alkali used in the reaction process of pentaerythritol diacrylate and alkyl substituted chloroacetyl chloride (IV) is selected from tertiary amine and steric secondary amine; triethylamine, tripropylamine, diisopropylethylamine are preferred. The mass ratio of the pentaerythritol diacrylate to the alkyl-substituted chloroacetyl chloride (IV) is selected from 1: 1.05-1.5. The reaction temperature in the step 1) is selected from-10-0 ℃.

The invention provides a preparation method of a compound shown in formula (I), which is characterized in that a catalyst for esterification in the step 2) is selected from basic compounds, preferably potassium carbonate and triethylamine. The amount ratio of the compound of formula (II) to the 4-thioxanthone carboxylic acid species is selected from 1-1.1: 1; the mass ratio of catalyst to 4-thioxanthone carboxylic acid is selected from 1.1-2: 1; the reaction temperature of the ester of step 2) is selected from 45-75 ℃.

The preparation method of the compound shown in the formula (I) is characterized in that the polymerization inhibitor used in the step 2) is selected from hydroquinone, p-hydroxyanisole, BHT and anhydrous copper sulfate, and the addition amount is selected from 100-10000 ppm.

The preparation method of the compound of formula (I) provided by the invention can also be carried out by the following reaction equation:

wherein: r is selected from H, C1-C4 alkyl.

The preparation method of the compound of formula (I) provided by the invention can also comprise the following steps:

1) reacting 4-thioxanthone formic acid with alkyl substituted methyl chloroacetate (V) under alkaline conditions to generate a compound shown in a formula (III);

2) the compound of formula (III) obtained in the step 1) is esterified with corresponding pentaerythritol diacrylate under the action of a catalyst and a polymerization inhibitor to obtain the compound of formula (I).

The alkali used in the reaction process of the 4-thioxanthone formic acid and the methyl chloroacetate in the step 1) is selected from tertiary amine and steric hindrance secondary amine; triethylamine, tripropylamine, diisopropylethylamine are preferred. The mass ratio of the 4-thioxanthone formic acid and the alkyl substituted methyl chloroacetate (V) is selected from 1: 1.1-2.0, wherein the dosage of the alkali is 1.1-1.5 times of that of the 4-thioxanthone formic acid substance.

The catalyst for the transesterification in step 2) is selected from basic compounds, preferably sodium methoxide, sodium tert-butoxide and potassium tert-butoxide. The reaction temperature of the ester exchange is selected from 95-130 ℃.

The polymerization inhibitor for the ester exchange reaction in the step 2) is preferably hydroquinone, p-hydroxyanisole, BHT and anhydrous copper sulfate, and the addition amount is preferably 100-10000 ppm.

The compound of the formula (I) shows excellent photocuring performance, high activity, low mobility and good compatibility with resin.

The specific implementation mode is as follows:

the invention will be further illustrated by the following non-limiting examples.

Example 1:

preparation of Compound A

Adding 48.8g of pentaerythritol diacrylate (0.2mol), 23.3g of triethylamine (0.21mol) and 240ml of dichloromethane into a three-necked bottle, carrying out electromagnetic stirring reaction, respectively connecting three mouths of the three-necked bottle with a thermometer, a drying tube and a constant pressure dropping funnel containing 46.3g of chloroacetyl chloride (0.41mol) and 120ml of dichloromethane, slowly dropwise adding at a low temperature, keeping the temperature between 0 and-5 ℃, and after dropwise adding, moving to room temperature for reaction. TLC monitored the reaction was complete. The triethylamine hydrochloride was filtered, washed 2-3 times with saturated sodium bicarbonate, washed with saturated brine, dried over anhydrous magnesium sulfate, and spin-dried. Separating and purifying with chromatographic column to obtain transparent oily matter with yield of 85% and purity not lower than 95%.¹H NMR(400MHz,CDCl₃)δ6.45(dd,1H),6.05(m,2H),5.58(dd，2H),4.34(s,4H),4.10(s,4H),4.00(s,4H)。

In a four-necked reaction flask equipped with mechanical stirring, 102.5g of thioxanthone-4-carboxylic acid (0.4mol), 60.8g of potassium carbonate (0.44mol), 500ml of DMF, 79.4g of pentaerythritol (diacryloyloxy) bis (2- (2-chloroacetoyloxy) ethyl ester) (0.2mol), 0.5g of hydroquinone were charged, heated to 65 ℃ and the completion of the reaction was monitored by TLC. Hot salt leachingPrecipitating, desolventizing the filtrate, and slowly cooling for crystallization to obtain 125.6g of light yellow crystals.¹H NMR(400MHz,CDCl₃)：δ8.23(d,2H)，7.79(d,1H)，7.60-7.28(m,10H)，6.25(d，2H)，6.05(m，2H)，5.59(d,2H)，5.21(s，4H)，4.12(s，4H)，4.00(s，4H)。MS：m/z[M+1]⁺＝837。

Example 2:

preparation of Compound B

Adding 48.8g of pentaerythritol di (acrylate) (0.2mol), 23.3g of triethylamine (0.21mol) and 240ml of dichloromethane into a three-necked bottle, carrying out electromagnetic stirring reaction, respectively connecting three mouths of the three-necked bottle with a thermometer, a drying tube and a constant pressure dropping funnel containing 51.6g of 2-chloropropionyl chloride (0.41mol) and 120ml of dichloromethane, slowly dropwise adding at low temperature, keeping the temperature between 0 and-5 ℃, and after dropwise adding, moving to room temperature for reaction. TLC monitored the reaction was complete. The triethylamine hydrochloride was filtered, washed 2-3 times with saturated sodium bicarbonate, washed with saturated brine, dried over anhydrous magnesium sulfate, and spin-dried. Separating and purifying with chromatographic column to obtain transparent oily matter with yield of 80% and purity not lower than 95%.¹H NMR(400MHz,CDCl₃)δ6.37(dd,1H),6.15(m,2H),5.54(dd，2H),4.45(q,2H),4.30(s,4H),4.10(s,4H),4.00(s,4H),1.73(d,6H)。

In a four-necked reaction flask equipped with mechanical stirring, 102.5g of thioxanthone-4-carboxylic acid (0.4mol), 60.8g of potassium carbonate (0.44mol), 500ml of dichloroethane, 85.1g of pentaerythritol bis (acryloyloxy) bis (2- (2-chloropropionyloxy) ethyl ester) (0.2mol), 0.6g of p-hydroxyanisole were charged, heated to 65 ℃ and the completion of the reaction was monitored by TLC. The salt precipitate was filtered off with suction while hot, the filtrate was desolventized and purified by column chromatography to give 103.8g of a pale yellow oil.¹H NMR(400MHz,CDCl₃)：δ8.31(d,2H)，7.69(d,1H)，7.53-7.32(m,10H)，6.20(d，2H)，6.00(m，2H)，5.56(d,2H)，5.21(s，4H)，4.97(q，2H),4.00(s，4H)，1.57(d，6H)。MS：m/z[M+1]⁺＝865。

Example 3:

preparation of

Adding 50.0g of thioxanthone-4-carboxylic acid, 250ml of tetrahydrofuran, 23.6g of triethylamine and 25.6g of methyl chloroacetate into a 500ml four-mouth bottle with mechanical stirring, heating to 50-60 ℃, reacting for 8 hours, carrying out suction filtration, cooling the filtrate to 0-5 ℃, stirring and crystallizing for 2 hours, carrying out suction filtration to obtain a crude product, recrystallizing the crude product with toluene, and drying to obtain 53.7g of yellow flaky crystals, wherein the yield is 84% and the content is more than or equal to 98.0%.

In a 500ml four-necked flask equipped with a mechanical stirrer and a water separator, 32.8g of methyl thioxanthone-4-formyloxyacetate, 0.3g of sodium methoxide, 200ml of methylcyclohexane, 13.5g of pentaerythritol diacrylate and 0.2g of p-hydroxyanisole were charged, and the mixture was heated to reflux and separated from methanol for 14 hours. Slowly cooling to separate out solid, filtering to obtain 24.2g of light yellow solid with the liquid phase content being more than or equal to 92 percent. MS: m/z [ M +1]⁺＝837

Example 4: evaluation of Performance

The photocurable composition was prepared in the formulation shown in Table 1, and the prepared photocurable composition was applied to a glass plate using a 22 μm wire bar coater. The coated sample was mounted on a belt and transported under a mercury lamp light source. Repeated indentation and scratching with fingernails did not produce prints as a complete cure standard, determining the belt speed for a fully cured sample.

Table 1: formula of photocuring system

The contrast substance A is of a structure

Contrast substance B is of structure

Contrast substance C as a structure

Contrast object D is in structure

(a fragment containing polyethylene glycol 400. sup. th-,

)

1. the curing speed evaluation results are shown in table 2:

table 2: evaluation results of curing speed

	Curing speed m/min
		Group 1	25
2 groups of	20
		Group 3	35
4 groups of	30
		5 groups of	25
6 groups of	45

From the results in Table 2, it can be seen that the photoinitiators prepared in the present application have a very good curing speed compared to the comparative initiators.

2. Migration evaluation

0.5g of EO3-TMPTA solution with the initiator mass fraction of 3% is weighed, ultrasonically treated for 30min, uniformly coated on a glass sheet (25mm multiplied by 75mm) with the thickness of 100um, and irradiated under a mercury lamp for 3-5min to completely cure. The glass plate with uniform mass film was soaked in a brown jar containing 50ml of chloroform for 4 days. After soaking, the UV absorption spectrum was tested. The mobilities of the example polymerizable photoinitiator and the control initiator were obtained according to the following formula:

C＝A/(εL)………………………………(1)

X＝m₁/m₂……………………………(2)

wherein: c, the concentration of the initiator in the extract liquor, mol/L;

a-absorbance;

epsilon-molar extinction coefficient, L/(mol. cm);

l-optical path length, cm;

x-percent residue,%;

m₁-residual mass of initiator, g;

m₂mass of initiator added, g

The results are shown in table 3:

table 3: evaluation results of initiator residue

	Percent initiator residue/%)
		Compound A	0.09
Compound B	0.07
		Control A	1.10
Comparative product B	0.80
		Control substance C	0.15
Reference substance D	0.23

Claims

1. A polymerizable photoinitiator having the structural formula (i):

wherein: r is selected from H, C1-C4 alkyl.

2. A polymerizable photoinitiator according to claim 1 wherein formula (i) is selected from the following structures:

3. a method of preparing a polymerizable photoinitiator according to claim 1, wherein the polymerizable photoinitiator is prepared by the steps of:

wherein: r is selected from H, C1-C4 alkyl,

1) pentaerythritol diacrylate reacts with a compound shown as a formula (IV) under alkaline conditions to generate a compound shown as a formula (II);

2) reacting the compound of the formula (II) obtained in the step 1) with corresponding 4-thioxanthone formic acid under the action of a catalyst and a polymerization inhibitor to obtain a compound of the formula (I);

wherein the alkali used in the reaction process of the pentaerythritol diacrylate and the compound shown in the formula (IV) in the step 1) is tertiary amine; the mass ratio of the pentaerythritol diacrylate to the compound feeding substance shown in the formula (IV) is 1: 1.05-1.5; step 1), the reaction temperature is-10-0 ℃;

the catalyst reacted in step 2) is selected from basic compounds; the amount ratio of the compound of formula (II) to the 4-thioxanthone carboxylic acid material is 1-1.1: 1; the mass ratio of the catalyst to the 4-thioxanthone carboxylic acid is 1.1-2: 1; the reaction temperature of the reaction in the step 2) is 45-75 ℃; the polymerization inhibitor used in the step 2) is selected from hydroquinone, p-hydroxyanisole, BHT and anhydrous copper sulfate, and the addition amount is 100-10000 ppm.

4. A method of preparing a polymerizable photoinitiator according to claim 3 wherein the base used in the reaction of pentaerythritol diacrylate with the compound of formula (IV) in step 1) is selected from triethylamine, tripropylamine, diisopropylethylamine.

5. A method of preparing a polymerizable photoinitiator according to claim 3 wherein the catalyst used in step 2) is selected from potassium carbonate and triethylamine.

6. A method of preparing a polymerizable photoinitiator according to claim 1, characterized in that it is prepared by the following steps:

wherein: r is selected from H, C1-C4 alkyl;

1) reacting 4-thioxanthone formic acid with a compound shown as a formula (V) under alkaline conditions to generate a compound shown as a formula (III);

2) carrying out ester exchange reaction on the compound of the formula (III) obtained in the step 1) and corresponding pentaerythritol diacrylate under the action of a catalyst and a polymerization inhibitor to obtain a compound of a formula (I);

the alkali used in the reaction process of the 4-thioxanthone formic acid and the compound shown in the formula (V) in the step 1) is selected from tertiary amine; the dosage ratio of the 4-thioxanthone formic acid to the compound feeding substance shown in the formula (V) is 1: 1.1-2.0, wherein the dosage of the alkali is 1.1-1.5 times of that of the 4-thioxanthone formic acid substance;

the catalyst for the ester exchange reaction in the step 2) is selected from alkaline compounds, and the reaction temperature of the ester exchange is 95-130 ℃;

and 2) selecting a polymerization inhibitor for the ester exchange reaction from hydroquinone, p-hydroxyanisole, BHT and anhydrous copper sulfate, wherein the addition amount is 100-10000 ppm.

7. A method of preparing a polymerizable photoinitiator according to claim 6 wherein the base used in the reaction of the 4-thioxanthone carboxylic acid of step 1) with the compound of formula (V) is selected from triethylamine, tripropylamine, diisopropylethylamine.

8. A method for preparing a polymerizable photoinitiator according to claim 6 wherein the catalyst for the transesterification in step 2) is selected from sodium methoxide, sodium tert-butoxide and potassium tert-butoxide.