Phosphorous-containing monomer composition and process for preparation

Abstract

The present invention relates to a monomer composition comprising 2-hydroxyethyl methacrylate phosphate (HEMA-P) and methyl methacrylate (MMA) and a process for preparation.

Description

[0001] 202400248 Foreign Filings - 1 -

[0002] Phosphorous-containing monomer composition and process for preparation

[0003] The present invention relates to a monomer composition comprising 2-hydroxyethyl methacrylate phosphate (HEMA-P) and methyl methacrylate (MMA) and a process for preparation.

[0004] Background of the Invention

[0005] Phosphorous-containing (meth)acrylates in general are well known adhesion promoters in applications like adhesives or coating resins providing improved adhesion to polar substrates. Additionally, these phosphorous-containing (meth)acrylates can improve the corrosion protection of coating formulations due to the improved adhesion to the substrate. Furthermore, phosphorous-based compounds are well known to improve flame-retardant properties. The incorporation of phosphorus-containing (meth)acrylates into polymeric resins leads to the formation of flame-retardant materials.

[0006] 2-Hydroxyethyl methacrylate phosphate (HEMA-P) is one specific example of a phosphate-functionalized monomer which is often used in dental adhesives and composites due to its ability to bond well with both tooth surfaces and restorative materials. Its hydrophilic nature enhances the adhesion to dentin and enamel.

[0007] In coatings and adhesives, HEMA-P can improve adhesion to metal surfaces and enhance the durability and stability of the coating. Its phosphate group contributes to better binding with metal substrates. HEMA-P is further used in hydrogels and other biomedical devices due to its biocompatibility. This makes it suitable for contact lenses and other medical implants.

[0008] In paints and coatings, it can be used to enhance adhesion, flexibility, and water resistance.

[0009] Furthermore, HEMA-P can be used to modify polymers, imparting improved hydrophilicity and adhesion properties, which can be beneficial in various industrial applications. These applications leverage the chemical functionality of HEMA-P, particularly its ability to form strong adhesive bonds and its compatibility with a range of materials.

[0010] The HEMA-P used in accordance with the present invention contains 70 wt% of phosphate components and 30 wt% of methyl methacrylate.

[0011] HEMA-P is commonly prepared from 2-hydroxyethyl methacrylate (HEMA) and phosphorous pentoxide (P4O10, also known as P2O5) as outlined in the following Scheme 1 .

[0012] Scheme 1 : 202400248 Foreign Filings - 2 - mono-HEMA-P

[0013] P4O10 + [mono-(2-methacryloyloxyethyl) phosphate]

[0014] HEMA di-HEMA-P

[0015] [bis(2-methacryloyloxyethyl) phosphate] by-products: mono-HEMA-PP di-HEMA-PP

[0016] [mono-(2-hydroxyethyl methacrylate) di-phosphate] [bis(2-methacryloyloxyethyl) di-phosphate]

[0017] This reaction does not only lead to the desired monoester mono-HEMA-P, but also forms the diester di- HEMA-P in equimolar amounts. Dependent on the reaction conditions, the formation of the monoester byproduct mono-HEMA-PP and of the diester by-product di-HEMA-PP is observed.

[0018] If the content of the monoester mono-HEMA-P shall be increased compared to di-HEMA-P, less HEMA should be used. A shortfall of HEMA in the reaction leads to an incomplete reaction / conversion and the formation of the pyrophosphates mono-HEMA-PP, di-HEMA-PP and pyrophosphoric acid.

[0019] The difference quantity of HEMA can be replaced by water that hydrolyses the pyrophosphoric acid to phosphoric acid, mono-HEMA-PP to mono-HEMA-P and phosphoric acid, and di-HEMA-PP to two mono- HEMA-P monomers.

[0020] The drawback here is that, if molar amounts of water are used, too much phosphoric acid is formed that cannot be easily separated from the final product.

[0021] A low amount of diester is desired, as the diesters (= dimers) function as crosslinkers. A high amount of monoester is advantageous for emulsion and solvent polymerization as higher amounts of the monomer mono-HEMA-P can be incorporated and less coagulation occurs. In addition, a higher P-content leads to increased flame-retardancy of the resulting polymeric material.

[0022] In plastic applications, a high crosslinker content can lead to brittle material.

[0023] Furthermore, the monoester mono-HEMA-P has a higher amount of free OH-groups. This is an advantage for all surface related applications like coatings and adhesives due to an increased interaction by hydrogen bonding. 202400248 Foreign Filings - 3 -

[0024] It was therefore an object of the present invention to provide a composition containing phosphorous- containing (meth)acrylates that is characterized by a high content of monoesters (mono-HEMA-P and mono-HEMA-PP) and a low content of crosslinkers, i.e. diester compounds (di-HEMA-P and di-HEMA- PP).

[0025] State of the Art

[0026] Saiz et al. (Polymer Preprints (1997), 38(2), 143-144) disclose the synthesis of a phosphate-containing monomer composition consisting of mono-HEMA-P, di-HEMA-P and a triester, but starting from HEMA and phosphorous oxy chloride (POCh) instead of P2O5.

[0027] Cong et al. (Yingyong Huaxue (2015), 32(6), 658-665) describe the synthesis of phosphate-containing monomer mixtures by using a specific catalyst system consisting of tungsten-containing species on activated charcoal as carrier. Based on the pore structure of the activated charcoal, a high monoester content can be reached. Cong is silent about the removal of the charcoal, i.e. the purification of the monomer mixture.

[0028] Chen et al. (Shanghai Coat, 2011 , 49(9):11-15) also use HEMA and P2O5 for the synthesis of a phosphorous-containing monomer mixture although the focus lies on the increase of the diester content. The synthesis used HEMA-P as dispersant in the reaction of HEMA, P2O5 and water.

[0029] JP3433633B2 discloses the extraction of a phosphorous-containing monomer mixture with dichloromethane, water and sodium carbonate. Subsequently, the aqueous phase was extracted again with dichloromethane and hydrochloride. During this procedure, the diester di-HEMA-P is enriched in the organic phase to give a ratio of diester to monoester of 49:1 .

[0030] A process for preparing HEMA-P with a high monoester and a low diester content is not described.

[0031] Park Eu Soo et al. ("Synthesis of Acryl Phosphate Antistatic Agent and Its Effect on the Antistatic, Thermal and Mechanical Properties of PMMA", Macromolecular Research, volume 15, no. 7, 1 December 2007 (2007-12-01), pages 617-622) discloses a process for preparing HEMA-P by reacting 2-HEMA with P2O5 in the presence of a stabilizer (0.16 mol%) at 50°C, where crude product besides HEMA-P also comprises di-HEMA-P, then adding methyl methacrylate (MMA) and a radical initiator to the crude product solution to provide a copolymer. HEMA-P is used in the co-polymer as antistatic agent.

[0032] The presentation "VISIOMER HEMA-P: AN OVERVIEW" discloses a composition of HEMA-P with 30% MMA but no process for preparation. 202400248 Foreign Filings - 4 -

[0033] Detailed description of the invention

[0034] The present invention is directed to a process for preparing a 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition consisting of:

[0035] (A) 60 wt% to 80 wt%, preferably 70 wt%, of 2-hydroxyethyl methacrylate phosphate (HEMA-P); and

[0036] (B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A), the process comprising the steps of:

[0037] (i-1) mixing 1 .8 equivalents to 2.2 equivalents of 2-hydroxyethyl methacrylate (HEMA) with methyl methacrylate (MMA), a stabilizer and 0.35 to 0.5 equivalents of water; or

[0038] (i-2) mixing 1 .8 equivalents to 2.2 equivalents of 2-hydroxyethyl methacrylate (HEMA) with methyl methacrylate (MMA) and a stabilizer;

[0039] (ii) cooling the mixture prepared in step (i-1) or (i-2);

[0040] (iii) adding 0.9 to 1 .1 equivalents, preferably 1 equivalent, of phosphorous pentoxide into the reaction mixture prepared in step (ii) in several portions;

[0041] (iv) after complete dosage of phosphorous pentoxide, warming the reaction mixture prepared in step (iii) to room temperature and, subsequently, heating it to a desired temperature and cooling it again to room temperature;

[0042] (v-1) adding 0.35 to 0.5 equivalents of water; or

[0043] (v-2) adding 0.7 to 1 .0 equivalents of water;

[0044] (vi) subsequently heating the mixture prepared in step (v-1) or (v-2) to a desired temperature and cooling it again to room temperature; and

[0045] (vii) optionally filling the product received in step (vi) into storage containers, such as glass bottles or drums, characterized in that the amount of water added in steps (i-1) and (v-1) versus (i-2) and (v-2) is in the range of 0.7 equivalents to at most 1 equivalent.

[0046] The content of each component (A) and (B) is based on the total weight of the 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition. In a particular embodiment, the proportions of components (A) and (B) add up to 100 wt%.

[0047] The stabilizer is selected from the group consisting of phenothiazine, 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPOL), 4-(meth)acryloyloxy-2, 2,6,6- tetramethylpiperidinyl-N-oxyl (TEMPOL-(meth)acrylate), hydroquinone monomethyl ether (HOME), 2,4- dimethyl-6-tert-butylphenol (DMBP), 2,4-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol (BHT) and mixtures thereof, preferably of phenothiazine, hydroquinone monomethyl ether (HOME), 2,4-dimethyl-6- tert-butylphenol (DMBP), 2,4-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol (BHT) and mixtures of these substances.

[0048] The stabilizer is used in amounts of 1 ppm to 6000 ppm, preferably 1 ppm to 3000 ppm, more preferably 1 ppm to 2000 ppm, based on the total amount of the components used as starting material. 202400248 Foreign Filings - 5 -

[0049] The reaction takes place at temperatures of 5°C to 60°C, preferably of 10°C to 50°C, more preferably of 15°C to 40°C.

[0050] The process is carried out in a suitable reaction vessel that is equipped with a stirrer, a solid dosing unit and a temperature control system and takes place under air conditions.

[0051] The reaction may be carried out at standard pressure.

[0052] The present invention is further directed to the process as outlined herein before, wherein the 2- hydroxyethyl methacrylate phosphate (HEMA-P) composition comprises:

[0053] (A) 60 wt% to 80 wt%, preferably 70 wt%, of 2-hydroxyethyl methacrylate phosphate (HEMA-P), comprising:

[0054] (a) at least 55 mol% of the monoesters 2-hydroxyethyl methacrylate phosphate (mono- HEMA-P) and 2-hydroxyethyl methacrylate di-phosphate (mono-HEMA-PP);

[0055] (b) 25 mol% or less of the diesters bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P) and bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP); and

[0056] (c) less than 20 mol% of the acids H3PO4 and H4P2O7; and

[0057] (B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A).

[0058] The content of each component (A) and (B) is based on the total weight of the 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition. In a particular embodiment, the proportions of components (A) and (B) add up to 100 wt%.

[0059] The content of each component (a), (b) and (c) is based on the total molar amount of the composition. In a particular embodiment, the proportions of components (a), (b) and (c) add up to 100 mol%.

[0060] The present invention is further directed to the process as outlined herein before, wherein the 2- hydroxyethyl methacrylate phosphate (HEMA-P) composition comprises:

[0061] (A) 60 wt% to 80 wt%, preferably 70 wt%, of 2-hydroxyethyl methacrylate phosphate (HEMA-P), comprising:

[0062] (a1) 45 mol% to 60 mol% of the monoester 2-hydroxyethyl methacrylate phosphate (mono-

[0063] HEMA-P);

[0064] (a2) 0 mol% to 10 mol% of the monoester 2-hydroxyethyl methacrylate di-phosphate (mono-

[0065] HEMA-PP);

[0066] (b1) 15 mol% to 20 mol% of the diester bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P);

[0067] (b2) 0 mol% to 5 mol% of the diester bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP);

[0068] (c1) 0 mol% to 15 mol%, preferably 5 mol% to 15 mol%, of H3PO4; and

[0069] (c2) 0 mol% to 5 mol% of H4P2O7; and

[0070] (B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A). 202400248 Foreign Filings - 6 -

[0071] The content of each component (A) and (B) is based on the total weight of the 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition. In a particular embodiment, the proportions of components (A) and (B) add up to 100 wt%.

[0072] The content of each component (a1), (a2), (b1), (b2), (c1) and (c2) is based on the total molar amount of the composition. In a particular embodiment, the proportions of components (a1), (a2), (b1), (b2), (c1) and (c2) add up to 100 mol%.

[0073] The present invention is further directed to a 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition, comprising:

[0074] (A) 60 wt% to 80 wt%, preferably 70 wt%, of HEMA-P, comprising:

[0075] (a) at least 55 mol% of the monoesters 2-hydroxyethyl methacrylate phosphate (mono- HEMA-P) and 2-hydroxyethyl methacrylate di-phosphate (mono-HEMA-PP);

[0076] (b) 25 mol% or less of the diesters bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P) and bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP); and

[0077] (c) less than 20 mol% of the acids H3PO4 and H4P2O7; and

[0078] (B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A).

[0079] The content of each component (A) and (B) is based on the total weight of the 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition. In a particular embodiment, the proportions of components (A) and (B) add up to 100 wt%.

[0080] The content of each component (a), (b) and (c) is based on the total molar amount of the composition. In a particular embodiment, the proportions of components (a), (b) and (c) add up to 100 mol%.

[0081] The present invention is further directed to a 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition, comprising:

[0082] (A) 60 wt% to 80 wt%, preferably 70 wt%, of HEMA-P, comprising:

[0083] (a1) 45 mol% to 60 mol% of the monoester 2-hydroxyethyl methacrylate phosphate (mono-

[0084] HEMA-P);

[0085] (a2) 0 mol% to 10 mol% of the monoester 2-hydroxyethyl methacrylate di-phosphate (mono-

[0086] HEMA-PP);

[0087] (b1) 15 mol% to 20 mol% of the diester bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P);

[0088] (b2) 0 mol% to 5 mol% of the diester bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP);

[0089] (c1) 0 mol% to 15 mol%, preferably 5 mol% to 15 mol%, of H3PO4; and

[0090] (c2) 0 mol% to 5 mol% of H4P2O7; and

[0091] (B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A).

[0092] The present invention is intended to be described in more detail below using the examples and comparative examples, without this giving rise to any restriction. 202400248 Foreign Filings - 7 -

[0093] Experimental part

[0094] Abbreviations

[0095] CE comparative example di-HEMA-P bis(2-methacryloyloxyethyl) phosphate di-HEMA-PP bis(2-methacryloyloxyethyl) di-phosphate HEMA 2-hydroxyethyl methacrylate mono-HEMA-P mono-2-hydroxyethyl methacrylate phosphate mono-HEMA-PP mono-2-hydroxyethyl methacrylate di-phosphate

[0096] MMA methyl methacrylate

[0097] The following chemicals were used for the preparation of the HEMA-P samples:

[0098] HEMA 98 from the company Rohm GmbH, MMA from the company Rohm GmbH, phosphorous pentoxide from the company ABCR GmbH

[0099] Analytical methods

[0100] NMR method

[0101] The composition of the phosphorous-containing monomer mixture was determined by a31P NMR measurement in DMSO-de solvent on a Bruker Avance 400 spectrometer. Corresponding shifts of the components are disclosed in the following Table 1 .

[0102] Table 1 :31P-NMR data of different components in the phosphorous-containing monomer mixture.

[0103] General Equipment for the HEMA-P experiments

[0104] For the reaction, a round bottom flask with 5 openings was used. The flask was equipped with a saber stirrer, reflux cooler, Pt100 temperature sensor, data logger and an air inlet. An Erlenmeyer flask with silicone hose was also connected to the apparatus for manual phosphorous pentoxide dosage. The reaction was cooled using a water bath. 202400248 Foreign Filings - 8 -

[0105] Preparation of HEMA-P comprising 30 wt% of MMA

[0106] Example 1

[0107] HEMA (234 g, 1.8 mol, 2 equivalents), water (6.8 g, 0.4 mol, 0.4 equivalents), MMA (161 g, 30 wt%) and an appropriate stabilizer amount were mixed together in a round bottom flask and the mixture was cooled with a water bath. Phosphorous pentoxide (132 g, 0.9 mol, 1 equivalent) was charged into the Erlenmeyer flask and dosed into the reaction mixture manually in several portions. The temperature during dosage did not exceed 40°C. After complete dosage, the reaction mixture was heated to 40°C for 1 .5 hours and, subsequently, the mixture was cooled again. Water (4.6 g, 0.3 mol, 0.3 equivalents) was slowly added to the mixture and it was heated to 40°C for another 2.5 hours. After cooling to room temperature, a sample of the resulting product mixture was taken for NMR analysis.

[0108] Comparative Example 1

[0109] HEMA (326 g, 2.5 mol, 2 equivalents), MMA (223 g, 30 wt%) and an appropriate stabilizer amount were mixed together in a round bottom flask and the mixture was cooled with a water bath. Phosphorous pentoxide (183 g, 1.3 mol, 1 equivalent) was charged into the Erlenmeyer flask and dosed into the reaction mixture manually in several portions. The temperature during dosage did not exceed 40°C. After complete dosage, the reaction mixture was heated to 40°C for 1 hour. Subsequently, additional HEMA (216 g, 1.7 mol, 1.3 equivalents) was dosed in several portions into the reaction mixture. After the addition was completed, the mixture was stirred at 40°C for another 3 hours. A sample for NMR analysis was taken.

[0110] Comparative Example 2

[0111] HEMA (265 g, 2.0 mol, 4 equivalents), MMA (142 g, 30 wt%) and an appropriate stabilizer amount were mixed together in a round bottom flask and the mixture was cooled with a water bath. Phosphorous pentoxide (71 g, 0.5 mol, 1 equivalent) was charged into the Erlenmeyer flask and dosed into the reaction mixture manually in several portions. The temperature during dosage did not exceed 40°C. After complete dosage, the reaction mixture was heated to 40°C for 5 hours and subsequently the mixture was cooled to room temperature again. A sample for NMR analysis was taken.

[0112] Comparative Example 3

[0113] HEMA (234 g, 1.8 mol, 2 equivalents), water (6.8 g, 0.4 mol, 0.4 equivalents), MMA (161 g, 30 wt%) and an appropriate stabilizer amount were mixed together in a round bottom flask and the mixture was cooled with a water bath. Phosphorous pentoxide (132 g, 0.9 mol, 1 equivalent) was charged into the Erlenmeyer flask and dosed into the reaction mixture manually in several portions. The temperature during dosage did not exceed 40°C. After complete dosage, the reaction mixture was heated to 40°C for 1 .5 hours and subsequently the mixture was cooled again. Water (3.2 g, 0.2 mol, 0.2 equivalents) was slowly added to the mixture and it was heated to 40°C for another 2.5 hours. After cooling to room temperature, a sample for NMR analysis was taken. 202400248 Foreign Filings - 9 -

[0114] Comparative Example 4

[0115] A sample of HEMA-P in MMA (143 g) prepared according to example 1 was further treated with additional water (1 .7 g, 0.1 mol) and stirred for additional 3 hours at 40°C. After cooling to room temperature, a sample for NMR analysis was taken. An overview of the examples and the experimental parameters are given in the following Table 2.

[0116] Table 2: Overview of important experimental parameters The resulting compositions are shown in the following Table 3.

[0117] Table 3: Compositional data of all phosphorous-containing compounds in the phosphorous- containing monomer mixture. 202400248 Foreign Filings - 10 -

[0118] Table 3 shows that in the presence of MMA the reaction of stoichiometric or even over-stoichiometric amounts of HEMA, namely 3 or 4 equivalents (see comparative examples 1 and 2) with 1 equivalent of phosphorous pentoxide led to roughly a 1 :1 mixture of mono- versus diester content.

[0119] Both examples show very high amounts of the diester di-HEMA-P. This can be reduced by the partial exchange of HEMA with water. An addition of 0.6 equivalents of water resulted in a decrease of the diester amount (see comparative example 4). When more than 1 equivalents of water were added, the content of phosphoric acid became too high (see comparative example 5).

[0120] Example 1 shows that the use of 2 equivalents HEMA and 0.7 equivalents of water split into two portions led to the desired composition with high amounts of monoester mono-HEMA-P and low amounts of diester di-HEMA-P.

Claims

202400248 Foreign Filings - 11 -Claims1. A process for preparing a 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition, comprising:(A) 60 wt% to 80 wt%, preferably 70 wt%, of 2-hydroxyethyl methacrylate phosphate (HEMA-P); and(B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A), the process comprising the steps of:(i-1) mixing 1 .8 equivalents to 2.2 equivalents of 2-hydroxyethyl methacrylate (HEMA) with methyl methacrylate (MMA), a stabilizer and 0.35 to 0.5 equivalents of water; or(i-2) mixing 1 .8 equivalents to 2.2 equivalents of 2-hydroxyethyl methacrylate (HEMA) with methyl methacrylate (MMA) and a stabilizer;(ii) cooling the mixture prepared in step (i-1) or (i-2);(iii) adding 0.9 to 1 .1 equivalents, preferably 1 equivalent, of phosphorous pentoxide into the reaction mixture prepared in step (ii) in several portions;(iv) after complete dosage of phosphorous pentoxide, warming the reaction mixture prepared in step (iii) to room temperature and, subsequently, heating it to a desired temperature and cooling it again to room temperature;(v-1) adding 0.35 to 0.5 equivalents of water; or(v-2) adding 0.7 to 1 .0 equivalents of water;(vi) subsequently heating the mixture prepared in step (v-1) or (v-2) to a desired temperature and cooling it again to room temperature; and(vii) optionally filling the product received in step (vi) into storage containers, such as glass bottles or drums, characterized in that the amount of water added in steps (i-1) and (v-1) versus (i-2) and (v-2) is in the range of 0.7 equivalents to at most 1 equivalent.

2. The process according to claim 1 , wherein the stabilizer is selected from the group consisting of phenothiazine, 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidinyl- N-oxyl (TEMPOL), 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPOL-(meth)acrylate), hydroquinone monomethyl ether (HOME), 2,4-dimethyl-6-tert-butylphenol (DMBP), 2,4-di-tert- butylphenol, 4-methyl-2,6-di-tert-butylphenol (BHT) and mixtures thereof.

3. The process according to claim 1 or 2, wherein the stabilizer is selected from the group consisting of phenothiazine, hydroquinone monomethyl ether (HOME), 2,4-dimethyl-6-tert-butylphenol (DMBP), 2,4- di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol (BHT) and mixtures of these substances.

4. The process according to claim 1 , 2 or 3, wherein the stabilizer is used in amounts of 1 ppm to 6000 ppm, preferably 1 ppm to 3000 ppm, more preferably 1 ppm to 2000 ppm, based on the total amount of the components used as starting material.202400248 Foreign Filings - 12 -5. The process according to any one of the preceding claims, wherein the 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition comprises:(A) 60 wt% to 80 wt%, preferably 70 wt%, of HEMA-P, comprising:(a) at least 55 mol% of the monoesters 2-hydroxyethyl methacrylate phosphate (mono- HEMA-P) and 2-hydroxyethyl methacrylate di-phosphate (mono-HEMA-PP);(b) 25 mol% or less of the diesters bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P) and bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP); and(c) less than 20 mol% of the acids H3PO4 and H4P2O7; and(B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A).

6. The process according to any one of the preceding claims, wherein the 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition comprises:(A) 60 wt% to 80 wt%, preferably 70 wt%, of HEMA-P, comprising:(a1) 45 mol% to 60 mol% of the monoester 2-hydroxyethyl methacrylate phosphate (mono-HEMA-P);(a2) 0 mol% to 10 mol% of the monoester 2-hydroxyethyl methacrylate di-phosphate (mono-HEMA-PP);(b1) 15 mol% to 20 mol% of the diester bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P);(b2) 0 mol% to 5 mol% of the diester bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP);(c1) 0 mol% to 15 mol% of H3PO4; and(c2) 0 mol% to 5 mol% of H4P2O7; and(B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A).

7. A 2-hydroxyethyl methacrylate phosphate (HEMA-P) composition, comprising:(A) 60 wt% to 80 wt%, preferably 70 wt%, of HEMA-P, comprising:(a1) 45 mol% to 60 mol% of the monoester 2-hydroxyethyl methacrylate phosphate (mono-HEMA-P);(a2) 0 mol% to 10 mol% of the monoester 2-hydroxyethyl methacrylate di-phosphate (mono-HEMA-PP);(b1) 15 mol% to 20 mol% of the diester bis(2-methacryloyloxyethyl) phosphate (di-HEMA-P);(b2) 0 mol% to 5 mol% of the diester bis(2-methacryloyloxyethyl) di-phosphate (di-HEMA-PP);(c1) 0 mol% to 15 mol% of H3PO4; and(c2) 0 mol% to 5 mol% of H4P2O7; and(B) 20 wt% to 40 wt%, preferably 30 wt%, of methyl methacrylate (MM A).

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