Patent Application
20130266737
The present invention relates to a polymerization catalyst, comprising at least two components, wherein at least one of those components is selected from the group of nitrogen containing heterocycles and/or their derivatives and at least one of those components is selected from the group of organic sulfonic acids and/or organic sulfonic acid derivatives, as well to compositions comprising said catalyst and use of said catalysts.
Electronic devices such as circuit boards, semiconductors, transistors, and diodes are often coated with materials such as epoxy resins for protection. Such coating materials are often cured on the surface of an electronic device by heat. But electronic devices often are sensitive to heat, and too much heat may adversely affect the performance of a device. It is also a problem in practice that a lot of energy is necessary for heating and/or the time which is necessary for polymerization and curing reaction is too long.
Further, if the coating material shrinks or expands significantly in response to heat, the device it coats may be warped. Thus, it is desirable to develop methods for curing coating materials at relatively low temperatures in short time periods and to develop coating materials that have a near-zero volume change upon heat treatment so as to minimize the possiblities of damaging the coated devices.
Therefore it is an ongoing effort in research departments to look for ways to reduce the temperature and improve the polymerization step.
It is known that acidic catalysts can contribute to solve the above mentioned problems. Acids may be relatively efficient polymerization catalysts. Depending on their amount it may be possible to reduce the temperature and improve the polymerization step.
However, in practical applications, such strong acids also may negatively contribute to the final polymerization result and it's practical properties. For example deterioration of chemical resistance and physical properties of the cured material may appear.
Therefore it is a special intention of the present invention, to achieve good polymerization results with lower amounts of acidic catalysts.
In particular when different polymerization products are possible it is necessary to have means to direct the polymerization reaction into a direction which is of advantage for the practical use.
For example, it has been known that during polymerization of benzoxazine monomers by curing reactions, two types of repeating units are accessible. One is the ether-type repeating unit and the other is the Mannich-type repeating unit. It has been considered that the ether-type is one of the final products and will not undergo any reaction under the polymerization conditions. On the other hand, the inventors discovered that the ether-type is not a stable final product, but an intermediate structure that forms in the first step predominantly and it undergoes a main chain rearrangement in the second step to give the corresponding Mannich-type structure as shown in scheme 1.
For various applications of such polymers to structural materials, sealant and adhesives, the polymer must be thermally stable as much as possible. A further transition step from one structure into another one could cause serious problems in many cases, especially when already applied in practical use. Therefore, efficient and selective formation of one stable product, e.g. the Mannich-type poly(benzoxazine) is extremely desireable.
Depending on the monomer structure the temperature required for the rearrangement from the ether-type to the Mannich-type structure can be very high, mostly still above 200° C. Even by usage of conventional polymerization catalysts such as phenols, carboxylic acids, organic sulfonic acids, amines, imidazoles, and phosphines the polymerization results are not satisfying in regard to specific aspects. Looking at the organic sulfonic acids, those are relatively efficient catalysts, whereas the efficacy strongly depends on the amount of use. If the concentration of the organic sulfonic acid is high enough this can lead to a smooth polymerization process at acceptable temperature. Otherwise it might be that the quality of the polymerization product and/or the cured material would have negative impact on the final product. This might lead to increased corrosion or further negative effects caused by the acid catalyst. Therefore, as already explained, in practical applications, amount of such strong acids must be reduced as much as possible in order to prevent deterioration of chemical resistance and physical properties of the cured material.
Lewis acids such as PCl5, TiCl4, AlCl3 are also known as highly active catalysts and may be used for such low temperature polymerization, too. However they are highly sensitive to moisture and cause formation of volatile, toxic, and corrosive impurities, avoiding their practical use.
Therefore it is a further target of the present invention to make available moisture- and air-tolerant catalyst-components, by which the polymerization/curing reaction can be carried out without caution to decomposition of the catalyst-component and resulting evolution of toxic and/or corrosive by-products.
Therefore it is an object of the present invention to make available a polymerization catalyst, which is able to catalyze polymeric reactions at acceptable low temperature and at the same time leads to a decrease of negative impacts by the catalyst(s) used in the system.
Consequently one subject of the present invention is a polymerization catalyst, comprising at least two components, wherein
In a preferred embodiment the molar ratio of said nitrogen containing heterocycles and/or their derivatives to said organic sulfur containing acids and/or derivatives of organic sulfur containing acids in the polymerization catalyst according to the present invention are from 10:1 to 1:10, preferable from 3:1 to 1:3.
These ranges are preferred to achieve the best effect of the catalyst according to the present invention. In particular the main chain rearrangement from ether type to Mannich type structure will be improved in these ranges, giving a polymer product with less contamination by ether-type polybenzoxazine.
The nitrogen containing heterocycles according to the present invention can be saturated, unsaturated, or aromatic. Besides the above mentioned imidazoles it may also be preferred that the nitrogen containing heterocycles are a thiazole, an oxazole, an imidazole, a pyridine, a piperidine, or a pyrimidine, a piperazine, a pyrrole, an indole or a benzthiazolyl. It is furtheron preferred that there is no acidic functional group present at the nitrogen containing heterocycles.
Most preferably, the nitrogen containing heterocyclic moiety is a thiazole and/or an imidazole. In particular it is preferred that the nitrogen containing heterocycles and/or their derivatives according to the present invention are selected from the group of imidazoles and/or imidazole derivatives with formula I
with
R1, R2, R3 and R4 being hydrogen or aliphatic or aromatic hydrocarbons, whereas it is especialle preferred that said imidazole is selected from the group of imidazole, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1,2-dimethyl imidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole or 1-aminoethyl-2-methylimidazole.
Furtheron it is preferred, that the organic sulfur containing acids and/or derivatives of organic sulfur containing acids according to the present invention are selected from the group of sulfonic acids according to formula II
wherein R5 is preferably selected from aromatic groups, alkyl groups and fluorinated alkyl groups. In particular the organic sulfonic acid of the present invention is selected from the group of sulfonic acids according to formula III, IV, V and VI.
It is also of advantage in the sense of the present invention, that the at least two components of the inventive polymerisation catalyst are stable to moisture and air and most preferably also any potential further components in the polymerization catalyst are stable to moisture and air (or moisture- and air-tolerant). This allows to perform polymerization/curing reactions at lower temperature without decomposition of the catalyst-component upon exposure to moisture and air. In particular the inventive catalyst allows to achieve the thermodynamical stable final product of the polymerization/curing reaction at lower temperature than by usage of only a single catalytic component out of the catalytic components according to the present invention.
Another subject of the present invention is a curable composition comprising at least one polymerization catalyst according to the present invention in combination with at least one polymerizable component. It is preferred that the curable composition can be used to form a polybenzoxazine (PBO) composition. The preferred PBO composition contains a PBO and a catalyst according to the present invention and optionally an epoxy resin and/or a phenolic resin.
An example of an epoxy resin is epoxy cresol novalac. The molding composition may include, for example, about 0.5 weight % to about 7.0 weight %, preferably about 1.5 weight % to 3.5 weight %, of the epoxy resin.
An example of a phenolic resin is phenolic novalac. The molding composition may include, for example, 0.1 weight % to 3.0 weight %, preferably 0. 3 weight % to 1.5 weight %, of the phenolic resin.
In particular it is preferred, that the at least one polymerizable component according to the present invention is a benzoxazine component, in particular a component according to formula VII:
wherein
R6═H;
R7 is a linear or branched substituted or non substituted alkyl or aromatic group, R8, R9, R10 are independently selected from hydrogen, linear or branched substituted or non substituted alkyl, preferably with less than 12 C-atoms and aromatic group, whereas R16 preferably is an aromatic group;
R7 and R8 or R8 and R9 can optionally form a cyclic structure.
In particular polybenzoxazines (PBO) can be used, to provide a coating on electronic devices such as circuit boards and semiconductors. The preferred PBO compositions have high glass transition temperature, good electrical properties (e.g., dielectric constant), low flammability, and a near-zero percent shrinkage and expansion upon demolding, postcuring, and cooling.
Preferably the at least one benzoxazine component according to formula VII with R7, R8, R9, and R10 comprises a further benzoxazine structure represented as
wherein R6′, R7′, R8′, R9′, and R10′ are selected from hydrogen, linear or branched substituted or non substituted alkyl group and aromatic group.
It is furtheron preferred that the inventive composition comprises at least one benzoxazine component selected from
wherein R is a linear or branched substituted or non substituted alkyl or aromatic group and preferably R is a aromatic group;
It is furtheron a preferred composition, that the molar ratio between said one or more of the polymerizable component(s) according to the present invention and the polymerisation catalyst(s) according to the present invention is 90:10 to 99.9:0.1 preferably 95:5 to 99.5:0.5.
The benzoxazine-containing molding compositions can be prepared by any conventional methods. For example, the ingredients (including resins and other additives) can be finely ground, dry blended, densified on a hot differential roll mill, and then followed by granulation. The molding composition, as described above, can be used for coating electronic devices such as semiconductors or circuit boards. The prepared compositions can be molded by any suitable molding apparatus. An example of such an apparatus is a transfer press equipped with a multi-cavity mold. For more detail on methods for preparing molding compositions and for coating electronic devices, see U.S. Pat. No. 5,476,716. Below are some examples of other additives that can be included in the molding composition and the preferred ranges of their weight percent in the composition:
(1) A flame retardant such as a brominated epoxy novolac flame retardant (e.g., BREN, available from Nippon Kayaku). The preferred molding composition can contain up to 3.0 wt %, more preferably, 0.1-1.0 wt % of a flame retardant.
(2) A flame retardant synergist such as Sb 2 O 5 or WO 3. The preferred molding composition can contain up to 3.0 wt %, more preferably, 0.25-1.5 wt % of a flame retardant synergist.
(3) A filler such as silica, calcium silicate, and aluminum oxide. The preferred molding composition can contain 70-90 wt %, more preferably, 75-85 wt % of a filler.
(4) A colorant such as carbon black colorant. The preferred molding composition can contain 0.1-2.0 wt %, more preferably, 0.1-1.0 wt % of a colorant.
(5) A wax or a combination of waxes such as carnauba wax, paraffin wax, S-wax, and E-wax. The preferred molding composition can contain 0.1-2.0 wt %, more preferably, 0.3-1.5 wt % of a wax.
(6) Fumed silica such as aerosil. The preferred molding composition can contain 0.3-5.0 wt %, more preferably, 0.7-3.0 wt % of fumed silica.
(7) A coupling agent such as the silane type coupling agent. The preferred molding composition can contain 0.1-2.0 wt %, more preferably, 0.3-1.0 wt % of a coupling agent.
Also preferred is a composition wherein said composition comprises at least one additional solvent, preferably selected from ethers, ketones, esters, chlorinated hydrocarbons, aromatics, amides, alcohols, in particular selected from ester-type solvents and ketone-type solvents.
When it comes to curing temperatures it is preferred that the compositions according to the present invention are curable at a temperature from 100° C. to 250° C., preferably from 130° C. to 180° C., in particular from 130 to 160° C.
When it comes to curing pressures it is preferred that the compositions according to the present invention are curable at a pressure between 1 to 100 atm, preferably under atmospheric pressure.
Compositions according to the present invention preferably are comprising 20% by weight to 99.9% by weight, more preferably 40% by weight to 99.5% by weight, most preferably 50% by weight to 99% by weight of one or more of the accordingly included polymerizable component(s) relative to the total composition.
A further subject of the present invention is a copolymerization and/or a polymerization product which is achievable by curing of a composition according to the present invention.
In particular it is preferred to arrive at a copolymerization and/or a polymerization product by following the present invention, wherein by coming from one or more benzoxazine monomer(s) a greater part of the Mannich-type structure is made available than by usage of a polymerization catalyst, comprising only one catalytic component selected from the group of nitrogen containing heterocycles and/or their derivatives or from the group of organic sulfur containing acids and/or derivatives of organic sulfur containing acids.
It is preferred, that the portion of the Mannich-type structure in the copolymerization and/or a polymerization product according to the present invention is higher than 50 weight %, more preferably higher than 70 weight %, most preferably higher than 90 weight % related to the total weight of the copolymerization and/or polymerization product.
Preferably the copolymerization and/or a polymerization product according to the present invention comprises at least one polymerization catalyst according to the present invention.
A copolymerization and/or a polymerization product according to the present invention can preferably be produced by usage of a range of curing temperature from 100° C. to 200° C., more preferably from 130° C. to 180° C., most preferably from 130° C. to 160° C.
In a preferred embodiment a composition and/or a copolymerization and/or a polymerization product according to the present invention is in the form of an adhesive, in which case one or more of an adhesion promoter, a flame retardant, a filler, a thermoplastic additive, a reactive or non-reactive diluent, and a thixotrope might be included. In addition, such an inventive adhesive may be placed in film form, in which case a support constructed from nylon, glass, carbon, polyester, polyalkylene, quartz, polybenzimidazole, polyetheretherketone, polyphenylene sulfide, poly p-phenylene benzobisoaxazole, silicon carbide, phenolformaldehyde, phthalate and napthenoate may be included.
The inventive compositions and/or a copolymerization and/or a polymerization products (and pregregs and towpregs prepared therefrom) are particularly useful in bonding of composite and metal parts, core and core-fill for sandwich structures and composite surfacing, and in the manufacture and assembly of composite parts for aerospace and industrial end uses, such as matrix resins for fiber reinforced composite articles, as matrix resins for use in prepregs, or as matrix resins in advanced processes, such as resin transfer molding and resin film infusion.
It is a further subject of the present invention to make use of at least one polymerization catalyst according to the present invention in curable compositions comprising at least one benzoxazine component, which in a preferred embodiment is covered by formula VII:
wherein
R6═H;
R7 is a linear or branched substituted or non substituted alkyl or aromatic group, R8, R9, R10 are independently selected from hydrogen, linear or branched substituted or non substituted alkyl and aromatic group, whereas R10 preferably is a aromatic group;
R7 and R8 or R8 and R9 can optionally form a cyclic structure.
In another preferred embodiment of the inventive use according to the present invention the at least one benzoxazine component according to formula VII with R7, R8, R9, and R10 comprises a further benzoxazine structure represented as
wherein R6′, R7′, R8′, R9′, and R10′ are selected from hydrogen, linear or branched substituted or non substituted alkyl group and aromatic group.
In particular the inventive use is fulfilled with a composition comprising at least one benzoxazine component selected from
Wherein R is a linear or branched substituted or non substituted alkyl or aromatic group, preferably R is a aromatic group;
In regard to the inventive use it is also preferred to have a molar ratio between the at least one benzoxazine component according to the inventive use and the at least one catalyst according to the present invention of 90:10 to 99.9:0.1 and preferably from 95:5 to 99.5:0.5.
It is also preferred, that the compositions to be used according to the present invention comprise at least one additional solvent, preferably selected from ethers, ketones, esters, chlorinated hydrocarbons, aromatics, amides, alcohols, in particular selected from ester-type solvents and ketone-type solvents.
In another preferred embodiment of the inventive use the composition is curable at a temperature from 100° C. to 250° C., more preferably from 130° C. to 180° C., most preferably from 130 to 160° C.
It is also preferred in connection with the inventive use to have compositions which are curable at a pressure between 1 to 100 atm, more preferably under atmospheric pressure.
In the composition to be applied in the inventive use it is preferred to have one or more of the accordingly included polymerizable component(s), in particular benzoxazine components in a concentration from 20% by weight to 99.9% by weight, more preferably 40% by weight to 99.5% by weight, most preferably 50% by weight to 99% by weight relative to the total composition.
Preferably the final compositions for the inventive use comprise additional components selected from the groups of inorganic fillers preferably silica powder, powdery metal oxide, and powdery metal or organic fillers preferably rubber particle and other polymer particles.
It is a further subject of the present invention to use curable compositions according to the present invention or a copolymerization and/or a polymerization products according to the present invention achievable from those inventive compositions, in the preparation of and/or as sealants, adhesives and/or coatings, preferably in electronic chip bonding and electronic chip underfills, whereby the sealants, adhesives and/or coatings are preferably applied to and hardened on or between substrates selected from the group comprising metals, silicates, metal oxides, concrete, wood, electronic chip material, semiconductor material and organic polymers.
In particular the curable compositions according to the present invention or a copolymerization and/or a polymerization product according to the present invention achievable from those inventive compositions are used for a variety of applications including adhesive and molded applications. Preferably the inventive use is directed to the application as adhesives where their low flammability is important (e.g. airplane interiors etc.) or where their thermal stability and easily modified physical properties such as modulus, tensile strength, and coefficient of expansion would be of value. As mentioned they could also be used in filled or unfilled molding applications,as matrix resins for fiber reinforced composite articles, as matrix resins for use in prepregs, or as matrix resins in advanced processes, such as resin transfer molding and resin film infusion.
A further subject of the present invention is a method of coating a device by heating a composition according to the present invention to a temperature sufficient to cure the composition, which preferably comprises a benzoxazine monomer, thus forming a polymer which coats a surface of the device, which is preferably an electronic device such as a semiconductor or a circuit board.
In case the composition comprises a benzoxazine monomer it is also preferred that the heating temperature is high enough to result in more than 50 weight %, more preferably more than 70 weight %, most preferably more than 90 weight % of the Mannich type structure related to the total weight of the copolymerization and/or polymerization product.
A further subject of the present invention is a device coated with a copolymerization and/or a polymerization product according to the present invention.
In a preferred embodiment the device can be an electronic device such as a semiconductor or a circuit board.
The present invention is exemplified in more detail by means of Examples, which follow below.
A benzoxazine according to scheme 1 (shown in
The resulting mixture was then heated at 150° C. The progress of the reaction according to scheme 1 was observed by continuous 1H-NMR analysis. Looking into
Regarding to example 1 the 1H-NMR spectra revealed, that the complete monomer was transformed into polymeric structure after 2 h heated at 150° C.
After that the heating of the mixture was continued to observe ongoing main chain rearrangement.
Further data are also incorporated in scheme 2, shown in
In a first comparative example the same conditions like in example 1 were used, with the only difference, that instead of a catalyst according to the present invention PTS (1 mol %)-EMI (1 mol %) a single catalyst was used, in detail 2 mol % PTS was used. Data are also incorporated in scheme 2.
From 1H-NMR-Monitoring it can be seen that the conversion of the monomer is quite rapid, as can be expected from the strong acidity of PTS (
In other words, replacement of a part of PTS with EMI allows not only reduction of the total acidity of the catalyst but also further improvement of the efficiency in main chain rearrangement.
In another comparative example also the same conditions like in example 1 were used, with the only difference, that instead of the inventive catalyst combination PTS (1 mol %)-EMI (1 mol %) a single catalyst 2 mol % EMI was used. Data are also incorporated in scheme 2.
It can easily be seen from the results compiled in
Further examples can be seen from scheme 2 (shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 06019841 | Sep 2006 | EP | regional |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12442316 | Jul 2009 | US |
| Child | 13557769 | US |
