EP4058511A1

EP4058511A1 - Curable composition

Info

Publication number: EP4058511A1
Application number: EP20803171.6A
Authority: EP
Inventors: Gerard Hubertus REESTMAN; Christian Biecker; Frederik Piestert; Thorsten Kröller
Original assignee: BYK Chemie GmbH; BYK Nederland BV
Current assignee: BYK Chemie GmbH; Altana Pharma BV
Priority date: 2019-11-14
Filing date: 2020-11-12
Publication date: 2022-09-21
Also published as: CN114729150A; JP2023502105A; WO2021094413A1

Abstract

Use of an inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof to compensate the viscosity-reducing effect of an acid-functional additive (b) in a composition comprising a polyester resin (c) and an inorganic thickening agent (d), which is different from the inorganic salt (a).

Description

CURABLE COMPOSITION

The present invention relates to the use of an inorganic salt to compensate the viscosity-reducing effect of an acid-functional additive in a composition comprising a polyester resin and an inorganic thickening agent. Furthermore, the present invention relates to said composition and a process of preparing a 3-dimensional article.

Thermoset resins such as unsaturated polyester resins are commonly employed in a wide variety of products, such as casting materials and fiber reinforced materials. Unsaturated polyester resins are usually condensation products of dicarboxylic acids or anhydrides with difunctional alcohols, to provide backbone unsaturation needed for crosslinking. During the crosslinking process, curing of the resin takes place. This process leads to an increase in viscosity and results in the hardening (curing) of the resin. Auxiliary components may further be added to improve the workability of the resin. One of those commonly employed auxiliary components are additives, for example process additives, which enhance the manufacturing process of resins in various ways and are indispensable to the manufacturing of thermoset resins. However, the thickening of curable systems like polyester resins is influenced by acids. Therefore, use of those additives, which are generally acidic ones, may under certain conditions lead to a retardation of the thickening time of the resin. The more acidic groups are added, the longer the thickening needs time. Therefore, there is an ongoing need to compensate the delay in thickening time and to adjust the curing process accordingly.

US 3,538,188 deals with thickening agents for polyester resins. A mixture of inorganic lithium and magnesium salts are added to an unsaturated polyester resin to increase the viscosity of the resin. The mixture inhibits the viscosity build up during the first 24-48 hours and thereafter causes a rapid high viscosity build up. However, it does not deal with the addition of additives nor their respective effects on the resin. US2007/00041 A1 deals with thickening agents for polyester resins used in Cured-ln-Place-Pipe open-molding processes. An active agent, comprising magnesium oxide and calcium oxide, is employed to increase the viscosity of the polyester resins. Again, the document does not cover the use of additives in such resin systems and therefore does not aim on diminishing their potentially occurring side effects.

It is therefore an aim of the present invention to overcome the drawbacks of the prior art and provide a compound that yields a reduced thickening time for workability. Other aims are to provide a compound that has to be employed in small amounts only, that is inexpensive, easy to use and increases the viscosity of the resin.

It was surprisingly found that the use according to the present invention fulfills the above-mentioned requirements.

The present invention relates to the use of an inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, to compensate the viscosity- reducing effect of an acid-functional additive (b) in a composition comprising a polyester resin (c) and an inorganic thickening agent (d), which is different from the inorganic salt (a).

In a further embodiment, the present invention relates to the use of an inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, to increase the viscosity of a composition comprising an acid-functional additive (b), a polyester resin (c) and an inorganic thickening agent (d), which is different from the inorganic salt (a).

Preferably, the inorganic salt (a) is a salt of an alkali metal or alkaline earth metal. Alkali metals comprise group 1 of the periodic table whereas the second group represents the alkaline earth metals. Examples for such alkali metal or alkaline earth metals are lithium, sodium, potassium, rubidium, beryllium, magnesium, calcium and strontium. It is preferred, that the inorganic salt (a) is a salt selected from the group of lithium, sodium, potassium, magnesium and calcium. It is more preferred that the inorganic salt (a) is a salt selected from the group of sodium, potassium and calcium. Even more preferred the inorganic salt (a) comprises a salt of calcium.

The inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions, and mixtures thereof. A halide ion is a halogen atom bearing a negative charge. The halide anions are fluoride (F ), chloride (Cl ), bromide (BG), iodide (G) and astatide (At ). Preferably, chloride, bromide or iodide anions are employed. More preferably, the inorganic salt (a) comprises chloride anions. Nitrate ions are ions with the molecular formula NO3^', phosphate ions are ions with the molecular formula (PO4)^3", sulfate ions have the molecular formula S0^2_ ₄ It is preferred, that the inorganic salt (a) comprises anions, which are selected from sulfate ions and halide ions. It is even more preferred that the inorganic salt (a) comprises halide ions. Preferably, the inorganic salt (a) comprises calcium chloride. In a different embodiment, the inorganic salt (a) consists of calcium chloride.

The composition comprises an acid-functional additive (b). Acid-functional additives are additives, which have acid-functional groups and show an acid- functionality. Salts of acids do not represent acid-functional additives according to the invention. The acid-functional additive (b) suitably comprises at least one of a carboxylic functional group, an acidic phosphate ester group, a phosphoric acid group and combinations thereof. More suitably, the acid-functional additive (b) comprises a first part which typically comprises a polyether, a polyester, a polyurethane, an epoxy-amine-adduct, a C10 to C100 alkyl chain which is linear or branched, or a combination thereof and a second part which comprises the acid-functional group. In a preferred embodiment of the invention the second part consists of the acid-functional group. In one preferred embodiment, the acid- functional group is a phosphoric acid ester group. Typically, the additive of such an embodiment is suitable as a wetting and dispersing agent. In another preferred embodiment, the acid-functional group is a carboxylic-acid group. The additive of such an embodiment is typically suitable as a processing and mold release agent. Generally, the acid-functional additive (b) has an acid value in the range of 10 to 250 mg KOH/g. Preferably, the acid-functional additive (b) has an acid value in the range of 10 to 200 g, more preferably in the range of 10 to 150 mg. Acid values may be calculated based on raw materials used or determined by titration. The acid value is the KOH quantity in mg that is required for neutralizing 1 g of substance. The acid values were determined by a neutralization reaction with a 0.1 N KOH in Ethanol according to DIN EN ISO 2114. i (

OH OK It is preferred, that the acid-functional additive (b) has a number average molecular weight of 300 - 15000 g/mol. It is more preferred, that the acid- functional additive (b) has a number average molecular weight of 300 to 10000 g/mol, even more preferred 300 to 7000 g/mol. It is most preferred, that the acid- functional additive (b) has a number average molecular weight of 300 to 5000 g/mol. The number average molecular weight can be determined by gel permeation chromatography (eluent: solution of lithium bromide (content 5 g/l) in dimethylacetamide, standard: polymethylmethacrylate, column temperature: 50°C) according to DIN 55672 part 2 (year: 2016). The number average molecular weight may also be determined by calculation. Additionally, the number average molecular weight for small molecules up to 1000 g/mol may be determined by other methods such as mass spectroscopy or nuclear magnetic resonance spectroscopy.

The inorganic salt (a) is employed to compensate the viscosity-reducing effect of an acid-functional additive (b) in a composition comprising a polyester resin (c) and an inorganic thickening agent (d). Acid-functional additives (b) lead to an increase in time needed for the thickening of a polyester resin and can reduce the final level of viscosity achievable considerably. To counterbalance this unwanted effect, inorganic salt (a) is added which leads to an acceleration of the thickening. Compensation of the viscosity-reducing effect with regard to the present invention means, that the unwanted effect of increasing thickening time and also depressed thickening behavior is at least partially counterbalanced. By adding the inorganic salt (a), the thickening time may finally be even more reduced, partially reduced or exactly compensated for in comparison to polyester resins (c) without acid- functional additives (b) and inorganic salt (a). This said, compensating for the viscosity-reducing effect leads at least to an increase in viscosity of the polyester resin (c).

Preferably, the polyester resin (c) is an unsaturated polyester resin. Moreover, the composition suitably comprises an ethylenically unsaturated polymerizable monomer. The polyester resin may be any of those known in the prior art, which crosslink during a curing process. Curing is a chemical process that produces the toughening or hardening of a polymer material by cross-linking of polymer chains. The curing process can be conducted by any method known in the art. Curing can be performed at room temperature or at elevated temperatures. A crosslinking can take place by means of polyaddition, polycondensation, or polymerization reactions. Preferred curing processes are selected from radical or ionic polymerization reactions and polyaddition reactions.

Unsaturated polyester resins are resin systems that cure via a radical chain reaction of carbon-carbon double bonds. They suitably comprise monomers such as unsaturated compounds to which are bonded one or more ethylenically unsaturated groups, preferably vinyl, substituted vinyl, allyl, (meth)acrylate and (meth)acrylamide groups. The unsaturated polyester resins may be any of those known in the prior art; unsaturated polyester resins also comprise vinyl ester resins (preferably obtainable by reaction of epoxy resins with an unsaturated monocarboxylic acid). Suitable examples are polyesters of dienes such as dicyclopentadiene (DCPD resins) as well as polyesters of dicarboxylic acids and diols having a major amount of olefinic unsaturation, preferably 10 to 75 olefinic groups per 100 ester groups. Typical diols are ethylene glycol and propylene glycol. Typical unsaturated acids include maleic acid, fumaric acid, itaconic acid and phthalic acid which can also be incorporated into the polyester resin starting from the anhydrides, esters or halides of these acids. The curing of unsaturated polyester resins is preferably carried out in the presence of monomers. Preferably the monomer is an ethylenically unsaturated polymerizable monomer.

It is possible to use any ethylenically unsaturated monomer and ethylenically unsaturated oligomer conventionally used in unsaturated polyester resins, which can crosslink with an unsaturated polyester. The ethylenically unsaturated polymerizacle monomer is preferably selected from styrene and substituted styrenes (like alpha-methylstyrene), allyls, allyl benzene, (meth) acrylates, (meth)acrylamides, and olefinic compounds.

Optionally, these systems further comprise crosslinkers, such as di(meth)acrylates, di(meth)acrylamides, divinylbenzene, tri(meth)acrylates, tetra(meth)acrylates and so forth. Unsaturated polyester resin systems can preferably be cured in the presence of initiators (like peroxides or azoinitiators), optionally in the presence of accelerators such as tertiary amines or cobalt compounds (e.g., cobalt octoate or naphthenate). The curing process can be initiated at ambient temperature or at elevated temperatures, optionally by applying pressure to the system, such as in a mold.

The inorganic thickening agent (d) is different from the inorganic salt (a). Suitably, the inorganic thickening agent (d) is selected from basic metal oxides, metal hydroxides, and combinations thereof. Basic metal oxides are generally oxides that have a pH above 7. They are usually formed by reacting oxygen with metals, especially alkali metals and alkaline earth metals. Suitable examples of basic metal oxides are MgO, CaO, ZnO, BaO. Metal hydroxides are hydroxides of metals and are commonly known as strong bases with a pH above 7. Many metal hydroxides are made up from hydroxides ions and the ion of the particular metal that it is made up of. Suitably examples of metal hydroxides are Ca(OH)2_, Mg(OH)₂, Zn(OH)₂. It is preferred, that the inorganic thickening agent (d) is selected from alkali metals, alkaline earth metals and combinations thereof. Preferably, the inorganic thickening agent (d) comprises magnesium oxide. In a further embodiment, the inorganic thickening agent (d) comprises at least 50% by weight of magnesium oxide, calculated on the weight of the inorganic thickening agent (d). In an even further embodiment, the inorganic thickening agent (d) consists of magnesium oxide.

The present invention further deals with a composition comprising a) an inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, b) an acid-functional additive (b), c) a polyester resin (c), and d) an inorganic thickening agent (d), which is different from the inorganic salt (a).

In a preferred embodiment, the composition comprises i. 0.0001 to 1.0000 % by weight of an inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, ii. 0.0100 to 5.0000 % by weight of an acid-functional additive (b) iii. 10.0000 to 50.0000 % by weight of a polyester resin (c) iv. 0.1000 to 1.0000 % by weight of an inorganic thickening agent (d), which is different from the inorganic salt (a), v. 43.0000 to 89.8899 % by weight of components different from a) to d), wherein the % by weight are calculated on the total weight of the composition. Furthermore, the composition generally may comprise solid particles selected from fillers, pigments, fibers, flame retardants (e.g. AI(OH)3) and combinations thereof. The solid particles are different from the inorganic thickening agent (d) and inorganic salt (a).

Suitable fillers are for example customary finely powdered or granular fillers, and may include hydraulic silicates, chalk, kaolin, dolomite, barite, cement, talc, diatomaceous earth, wood meal, wood chips, clay, talc, silica powder, glass powder, glass beads, microcellulose, silica sand, river sand, marble waste, crushed stone or any combinations thereof.

Fiber reinforced composite materials comprise fibers embedded in a polymer matrix. The polymer matrix serves as binder between the fibers. The fibers generally improve the mechanical properties of composite material, as compared to the matrix polymer alone. The fibers may be inorganic or organic. Suitable fibers are glass fiber, carbon fiber, basalt fiber and polymeric fibers line cellulose, and fibers of polyethylene, polycarboxyl ic esters or polyamide. They can be in the form of short fibers, having a length of up to 5 cm, or in the form of milled fibers, but are preferably in the form of long fibers as individual rovings, webs of parallel rovings, fiber mats, fiber webs, fiber weaves or fiber knits. They may generally be employed up to 60 % by weight, based on the total weight of the composition. Carbon fibers include amorphous carbon fibers and graphite fibers. Carbon fibers produced from various starting materials are equally suitable, for example, carbon fibers prepared from polyacrylonitrile, pitch, or rayon. The carbon fibers may have undergone a chemical or mechanical surface pretreatment, for example with known sizing agents during fiber manufacture. Carbon fibers, which have not been subjected to specific pretreatments, may likewise be employed. Depending on the intended end use, the carbon fibers may be present as filament fibers, as staple fibers, or as chopped fibers. In some embodiments, the carbon fibers are present as a woven or non-woven fabric. On other embodiments, the carbon fibers are present as a roving.

All known kinds of pigments may be used in the composition according to the invention. Inorganic or organic pigments and mixtures thereof may suitably be employed. Typically, the organic pigments are color pigments. This refers to colored material made of organic compounds with pigment properties. In some embodiments, the inorganic and organic pigments may preferably be used up to 30% by weight, based on the total weight of the composition.

Additionally, the invention covers a process of providing a 3-dimensional article comprising the steps of providing the composition according to the present invention bringing the composition in a desired three-dimensional shape, and curing the composition.

Examples for three-dimensional shaped parts are components or parts of boats, tanks (e.g. for oil, water, chemical products), pipes and tubes (eg.g for drinking and waste water), wall covering and sheathing, caravans, bathroom and lavatory interior (e.g. sinks, bathtubs, shower trays), seats (e.g .for busses, trains, stadiums), parts for automotives like cars, trucks, tractors (e.g. radiator cowls, trunk lids, air deflectors, spoilers, attachment parts, roofs), doors, window and casement frames, profiles, battery housings, parts for wind power plants like blades, housings, and the like.

Suitably, the step of bringing the composition in a desired three-dimensional shape is carried out by introducing the composition in a mold.

Typical procedures comprise sheet molding compounding (SMC), bulk molding compounding (BMC), infusion molding (RIM - resin infusion molding, RTM - resin transfer molding), compression molding, VARI (vacuum applied resin infusion), filament winding, pultrusion, and autoclave curing.

Further components may be present in the composition, in particular such components that are typically used in manufacturing thermosetting resins. Examples of such components include UV stabilizers, mold release agents, and anti-foaming agents. It is further preferred, that the process includes the step of impregnating fibers with the composition according to the present invention.

The invention further deals with a process of controlling the viscosity of a composition comprising the steps of providing an inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, providing an acid-functional additive (b), - providing a polyester resin (c), providing an inorganic thickening agent (d), which is different from the inorganic salt (a), mixing the components. Mixing is combining the components and exerting shear force on the combined components. The step of mixing the components may be executed according to current processes known by the person skilled in the art. This may involve mixing by manual or electrical means inter alia. Suitably, the mixing step is carried out in an extruder.

EXAMPLES

General preparation of the formulations:

Polyester resins, polystyrene solutions and additives are mixed together before adding all remaining components like fillers, pigments, peroxides etc. The total formulation is then homogenized via mixing by hand. The mixture is subsequently stirred using a dissolver, TYPE Pendraulik 5HWM-FDe80N 12-2 fitted with a dissolver disc 40 ± 10mm under the following conditions: Dispersing for 60 sec. ± 10sec. at a speed of 930rpm ± 50rpm, then for further 120sec. ± 10sec. at a speed of 1865 rpm ± 125rpm (peripheral speed 3.9 ± 0.3 m / s) dispersed. The finished homogenized compound is converted into an aluminum cup, tightly closed and stored for 30 minutes ± 5 minutes at 30 ° C and temperature ± 5 ° C in a water bath.

The viscosity is measured with a Brookfield DV II + - measuring instrument using a spindle (type of spindle for measurement listed at the corresponding results) at rotational speed of 5upm - 30 rpm. All amounts are in parts per hundred resin [phr].

Table 1: Raw materials Experiment I

Table 2: Formulation of experiment I Table 3: Results of experiment I

Table 3 shows the time-dependent viscosity profile of a SMC formulation 1 with additional additives. By adding calcium chloride to the formulation, the time- dependent viscosity profile is improved (formulations 2 and 3). Therefore, adding calcium chloride to the SMC formulation leads to an increase in thickening time as well as to an overall increase of the end viscosity of the formulation. Experiment II

Table 4: Formulation of experiment II

Table 5: Results of experiment II

Table 5 shows the time-dependent viscosity profile of formulation 4, having a poor viscosity built-up. By adding 0.3 phr calcium chloride (formulation 5) to the formulation, the thickening time is accelerated and the end viscosity is increased. Experiment 111-1/ lll-ll

Table 6: Formulation of experiment lll-l Table 7: Formulation of experiment lll-ll

Table 8: Results of experiment lll-l

Table 9: Results of experiment ll-ll

Tables 8 and 9 compare the effects of different inorganic salts added in different concentrations (formulations 7 to 12). As a control, a formulation without inorganic salts is shown (formulation 6). All additionally added inorganic salts used in the examples 7 to 12 ensure to overcome the thickening inhibition and lead to an increase in thickening time as well as to an increase in the end viscosity.

Claims

1. Use of an inorganic salt (a) wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, to compensate the viscosity-reducing effect of an acid-functional additive (b) in a composition comprising a polyester resin (c) and an inorganic thickening agent (d), which is different from the inorganic salt (a).

2. The use according to claim 1 , wherein the inorganic salt (a) is a salt of an alkali metal or alkaline earth metal.

3. The use according to claim 1 or 2, wherein the inorganic salt (a) is a salt selected from the group of lithium, sodium, potassium, magnesium and calcium.

4. The use according to any one of the preceding claims, wherein the inorganic salt (a) comprises calcium chloride.

5. The use according to any one of the preceding claims, wherein the acid-functional additive (b) comprises at least one of a carboxylic functional group, an acidic phosphate ester group, a phosphoric acid group and combinations thereof.

6. The use according to any one of the preceding claims, wherein the acid-functional additive (b) has an acid value in the range of 10 to 250 mg KOH/g.

7. The use according to any one of the preceding claims, wherein the acid-functional additive (b) has a number average molecular weight of 300 to 15000 g/mol.

8. The use according to any one of the preceding claims, wherein the polyester resin (c) is an unsaturated polyester resin.

9. The use according to any one of the preceding claims, wherein the composition comprises an ethylenically unsaturated polymerizable monomer.

10. The use according to any one of the preceding claims, wherein the inorganic thickening agent (d) is selected from alkali metals, alkaline earth metals and combinations thereof.

11. The use according to any one of the preceding claims, wherein the inorganic thickening agent (d) is selected from basic metal oxides, metal hydroxides, and combinations thereof.

12. The use according to any one of the preceding claims, wherein the inorganic thickening agent (d) comprises magnesium oxide.

13. A composition comprising a) An inorganic salt (a), wherein the inorganic salt (a) comprises anions selected from halide ions, nitrate ions, phosphate ions, sulfate ions and mixtures thereof, b) An acid-functional additive (b), c) A polyester resin (c ), and d) An inorganic thickening agent (d), which is different from the inorganic salt (a).

14. The composition according to claim 13, wherein the composition comprises i. 0.0001 to 1.0000 % by weight of an inorganic salt (a) ii. 0.0100 to 5.0000 % by weight of an acid-functional additive (b) iii. 10.0000 to 50.0000 % by weight of a polyester resin (c) iv. 0.1000 to 1.0000 % by weight of an inorganic thickening agent (d), which is different from the inorganic salt (a), v. 43.0000 to 89.8899 % by weight of components different from (a) to (d), wherein the % by weight are calculated on the total weight of the composition.

15. A process of preparing a 3-dimensional article comprising the steps of providing the composition according to claim 13 or 14 - bringing the composition in a desired three-dimensional shape, and curing the composition.