Polycarbonate as a chemical foaming agent.

Abstract

1. A method comprising the steps of combining a polycarbonate thermoplastic with a decomposition initiator to decompose the polycarbonate; and heating the polycarbonate thermoplastic and the decomposition initiator to a temperature between 120°C and 250°C to release carbon dioxide; wherein the polycarbonate thermoplastic and the decomposition initiator are combined with one or more additional ingredients to form a heat activated material which foams as a result of the release of carbon dioxide.

Description

[Technical field]

[0001] The present invention relates to the use of polycarbonate polymers and / or oligomers in combination with other ingredients (i.e., decomposition activators) to enable the decomposition of the polycarbonate above ambient temperatures but below the melting point temperature of the polycarbonate to release carbon dioxide gas for use as a chemical blowing agent. [Background technology]

[0002] Chemical foaming agents or chemical foaming agents are commonly used in the manufacture of foamed articles. In foams produced via a heat activation process, a chemical blowing agent is usually compounded into the formulated product that is activated in a subsequent step when the composition is exposed to a high temperature above the compounding step. Often the blowing agent is in the form of particles that decompose and release gases when exposed to high temperatures. Nitrogen and carbon dioxide are the usual primary gases released, but in many cases additional gases are released as well. Physical blowing agents, such as plastic microspheres containing volatile liquids and solvents, are also often used as blowing agents as well.

[0003] Although solid particulate blowing agents are useful commercially, they have several potential deficiencies depending on the particular application of the blowing agent, including interactions and reactivity with the incoming formulated product, storage and shipping complications, flammability prior to compounding, odors present in the foamed product, and health concerns associated with exposure to the blowing agent (e.g., surrounding azodicarbonamide).

[0004] One consequence with chemical blowing agents, such as azodicarbonamide (branded Celogen® AZ) or benzenesulfonyl hydrazide (branded Celogen® OT), is that they can react with other components in the formulated product, reducing the shelf-life stability of the product prior to heat activation. This can compromise product compatibility (i.e., shelf-life reduction), especially when the product may be exposed to high temperatures during secondary processing, shipping, or storage. The secondary effect is usually a reduction in the foaming percentage, and often reduced adhesion to substrates where the foamed article is expected to have adhesive properties. Summary of the Invention [Problem to be solved by the invention]

[0005] Thus, there is a need and desire for chemical foaming agents suitable for products that are intended to foam as a result of heat activation and that, when incorporated into a formulation, are stable, non-flammable, safe to handle, and do not produce undesirable odor producing decomposition products or by-products. [Means for solving the problem]

[0006] The present teachings fulfill one or more of the above needs through the improved methods described herein.

[0007] In a first aspect, the teachings herein provide a method for forming a heat-activated material that foams as a result of the release of carbon dioxide, comprising combining a polycarbonate thermoplastic (e.g., thermoplastic polycarbonate) with a decomposition initiator to decompose the polycarbonate; heating the polycarbonate thermoplastic and the decomposition initiator to a temperature between 120°C and 200°C to release carbon dioxide; and combining the polycarbonate thermoplastic and the decomposition initiator with one or more additional ingredients.

[0008] In another aspect, the teachings herein provide a composition that includes a polycarbonate thermoplastic, a decomposition initiator for decomposing the polycarbonate, an optional solvent in which the polycarbonate is dissolved, and one or more additional ingredients for forming a heat-activated adhesive. The polycarbonate thermoplastic and the decomposition initiator are adapted to release carbon dioxide upon heating the composition to a temperature between 120° C. and 250° C.

[0009] The decomposition initiator may be an amine. The decomposition initiator may be dicyandiamide or dicyandiamide. The decomposition initiator may be a compound with a urea functionality, which may preferably be a substituted urea. The decomposition initiator may be a reaction product of bisphenol A epoxy and monoethanolamine. The decomposition initiator may be a metal halide. The decomposition initiator may be a blocked isocyanate. The decomposition initiator may be an ammonium salt. The decomposition initiator may be a metal phosphate salt. The decomposition initiator may be a metal stearate salt. The decomposition initiator may be a metal carbonate salt or a metal hydroxide. The decomposition initiator may be a metal acetylacetonate. The decomposition initiator may be a titanate complex. The decomposition initiator may be a metal triflate salt. The decomposition initiator may be an organophilic phyllosilicate. The polycarbonate may be dissolved in a suitable solvent to form a dissolved product. The solvent may be capable of subsequently reacting into a polymer composition. The solvent may be a liquid epoxy. The solvent may be a solid epoxy. The solvent may be a combination of liquid and solid epoxies. The solvent may be a polycarbonate polyol. The solvent may be a polycaprolactone polyol. The solvent may be an organic solvent, including, but not limited to, acetone, methyl ethyl ketone, diethyl ketone, toluene, or xylene.

[0010] In another aspect, the teachings herein provide a composition that includes, based on the total weight of the composition, at least 10 wt.% of an epoxy resin; at least 0.5 wt.% of a dicyandiamide; at least 0.5 wt.% of a substituted urea; and about 2-10 wt.% of a polycarbonate thermoplastic.

[0011] The weight ratio of dicyandiamide to the compound having a urea functionality, preferably a substituted urea, may be in the range of 1:0.5 to 1:1.5. The polycarbonate and decomposition initiator may be micromilled. [Brief description of the drawings]

[0012] [Figure 1] Displays a graph showing the amount of CO2 produced for various combinations of ingredients. [Figure 2A] The chemical structures and the relative levels of electron density and steric hindrance are shown. [Figure 2B] The chemical structures and the relative levels of electron density and steric hindrance are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The descriptions and illustrations provided herein are intended to familiarize those skilled in the art with the teachings, their principles, and their practical application. Those skilled in the art may adapt and apply the teachings in many forms that may be most appropriate to the requirements of a particular use. Thus, the specific embodiments of the teachings shown are not intended to be exhaustive or to limit the teachings. Therefore, the scope of the teachings should be determined not with reference to the above description, but instead with reference to the appended claims and the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and patent publications, are incorporated by reference for all purposes. Moreover, other combinations that may be gleaned from the following claims are possible, and such combinations are also hereby incorporated by reference into this written description.

[0014] This application claims the benefit of the filing date of U.S. Provisional Application No. 63 / 280,893, filed November 18, 2021, the contents of which are incorporated herein by reference in their entirety for all purposes.

[0015] Fundamental to the teachings herein is the understanding that polymeric or oligomeric polycarbonates (e.g., polycarbonate thermoplastics, thermoplastic polycarbonates) when combined with certain additional ingredients can initiate decomposition of the polycarbonate at temperatures well below its normal decomposition temperature (greater than 400° C.) to release carbon dioxide that functions as a blowing agent. At least one decomposition accelerator may be utilized to stimulate polycarbonate decomposition at low temperatures. The decomposition accelerator may be utilized as part of a compounded product that may typically be comprised of one or more polymers combined with additional additives.

[0016] Examples of suitable decomposition accelerators include, but are not limited to, amines and nitrogen-containing compounds. Examples of amines and nitrogen-containing compounds include tertiary amines, imidazoles, amine adducts, triazoles, amides, ureas, and ammonium derivatives. Examples of other suitable decomposition accelerators include metal chlorides, blocked isocyanates, metal phosphates, metal stearates, metal carbonates, metal hydroxides, metal acetylacetonates, titanate complexes, metal triflate salts, organophilic phyllosilicates, and other Lewis acids. The selection and amount of decomposition agent can determine the decomposition temperature range of the polycarbonate and the amount of carbon dioxide decomposition products.

[0017] The softening points of polycarbonate polymers are usually in the range of 150°C to 170°C depending on the molecular weight. Unless otherwise clearly indicated, the softening point is preferably the VICAT softening point determined according to ASTM D 1525 Rate B (50 N). Therefore, if there is a desire to incorporate polycarbonate into heat-activated materials that activate below these temperatures, it may be necessary to dilute the polycarbonate to allow incorporation by preventing the hardening of the formulated polymer composition during compounding. As one non-limiting example, to incorporate polycarbonate into an epoxide-functional heat-activated system, the polycarbonate may be dissolved as a solvent in a bisphenol A-based liquid epoxy. Since both polycarbonate and bisphenol A have a common monomer, there is good solubility of polycarbonate in standard liquid epoxy resins. Such solvents containing reactive functional groups have the advantage of having the ability to react into the polymer matrix during heat activation. Other epoxides containing organic aromaticity can serve as suitable solvents as well, for example, bisphenol F epoxy resin. Depending on the amount of liquid epoxy resin used to accomplish the dissolution, it may be possible to produce a dissolution product ranging from a viscous liquid to a non-coalescent solid at 23°C. The solid dissolution product may be in the form of pellets, granules or powder. The dissolution product may also be in the form of a liquid. Other epoxy resins may also be used as solvents, e.g. bisphenol F liquid resins or even solid epoxy resins. Combinations of epoxy resins may be used as solvents to optimize the physical state of the dissolution product.

[0018] Another method of incorporating polycarbonate polymer involves microgrinding or cryo-grinding the polycarbonate and a disintegrant. The resulting powders may then be mixed together to form a blowing agent. This blowing agent can be added to a heat-activated material to provide the foaming capability. A challenge with this approach can be obtaining polycarbonate particles small enough due to the impact resistance of polycarbonate.

[0019] As mentioned above, polycarbonate melts using epoxy as a solvent have particular utility for epoxy-based adhesives or foams. However, it is also possible that the same melt products can be combined with one or more suitable decomposition accelerators to cause foaming of non-epoxy-based materials. Similarly, micro-ground polycarbonate powders combined with decomposition agents can be used to foam non-epoxide functional materials.

[0020] The selection of epoxy as the solvent is particularly useful for the epoxy-based thermosetting materials mentioned above. However, it is envisioned that solvents other than epoxy may also be utilized to dissolve the polycarbonate material. An example of a solvent other than epoxy is polycarbonate polyol (brand Eternacoll PH200D®). The polycarbonate polymer may be dissolved in the polycarbonate polyol to form a dissolution product. Depending on the amount of polyol used, the dissolution product may be in the form of a viscous liquid or a non-coalescing solid. Less preferably, an organic solvent may be used to solvate the polycarbonate and then removed by evaporation. Known organic solvents may include acetone, methyl ethyl ketone, diethyl ketone, toluene, or xylene.

[0021] When polycarbonate, either in the form of a solid or liquid melt product, or in the form of a powder from microgrinding, is incorporated into a formulated heat-activated composition and combined with a decomposition agent, it can then produce a foamed article upon exposure to elevated temperatures.

[0022] The teachings herein advantageously utilize polycarbonate as a chemical foaming agent in the formulated composition via polycarbonate decomposition and the accompanying release of carbon dioxide. By itself, polycarbonate is a stable engineering polymer. However, when combined with other ingredients, particularly base, then the decomposition temperature can be significantly reduced. Importantly, it can be reduced to a temperature range that is useful for the generation of gas for heat-activated polymeric compositions. This temperature range is usually between 140°C and 250°C for foaming adhesive applications. Typical automotive adhesive applications are cured at 140°C to 250°C. This includes the temperature range that exists for curing electrocoats (e-coats) used, for example, in the automotive industry for corrosion protection of steel or other metals.

[0023] As mentioned above, the use of polycarbonate as a chemical blowing agent in adhesive formulations is accompanied by the release of carbon dioxide gas. If the adhesive is a thermosetting material, this release rate can be matched to the adhesive's curing kinetics. For example, a typical epoxy adhesive utilized in automotive construction includes a combination of epoxy resins cured with a latent amine such as dicyandiamide (e.g., Amicure® CG-325G). By itself, dicyandiamide does not react sufficiently to completely cure the epoxy resin over the entire temperature range of 140°C to 250°C currently used by most automotive manufacturers. This may be due in part to the latency of dicyandiamide, but also to the fact that there are thick metal parts that need to be joined in an automobile. It may also be related to the fact that the transfer of thermal energy required to give a sufficient cure of the composition can be impeded. For this reason, curing agent activators / accelerators are often used to lower the required cure temperature of the dicyandiamide curing agent by increasing the solubility of dicyandiamide in the epoxy matrix, thereby resulting in a faster reaction.

[0024] It is possible that choosing the right particle size and type of hardener and hardener accelerator can help optimize the curing kinetics. Furthermore, the right combination of hardener and hardener accelerator should be selected so that the carbon dioxide from polycarbonate decomposition can sufficiently foam the adhesive. If the selected combination of hardeners builds molecular weight in the material too quickly, the carbon dioxide may not be able to foam the material to the desired extent. On the other hand, if the selected combination of hardeners cures the epoxy resin too slowly, the carbon dioxide gas may diffuse out of the adhesive and not foam as much as desired, leading to the collapse of the foamed article.

[0025] Amines and amine derivatives have been found to be particularly suitable for lowering the decomposition temperature of polycarbonates. However, the amine or nitrogen-containing amine derivative chosen to lower the decomposition temperature of polycarbonates should be selected so as not to negatively interfere with the curing mechanism in the adhesive, especially with the product latency. For example, ethanolamine has been found to be a good decomposer for polycarbonates. However, the use of ethanolamine in a latent heat-activated epoxy system is expected to react during mixing or compounding if the materials being mixed have epoxide functionality. To address this deficiency, it is possible to encapsulate the ethanolamine with a shell that melts or otherwise decomposes the ethanolamine at a suitable temperature, thereby delivering the ethanolamine for accelerating the decomposition of polycarbonates.

[0026] Based on the foregoing, the base composition selected for polycarbonate decomposition may be selected in such a way that it can be added to a typical heat-activated adhesive without reacting during mixing or unacceptably shortening the shelf life or negatively affecting other adhesive properties such as adhesion, adhesion durability or mechanical properties. Particularly useful amine and nitrogen-containing compounds that can be used in latent epoxy adhesives to reduce the decomposition temperature of polycarbonate are dicyandiamide, compounds with urea functionality, preferably substituted urea compounds, such as Omicure® U52M (aromatic substituted urea, 4,4'-m-ethylenebis(phenyldimethylurea)) from Huntsman Corporation, amine adducts, such as Ancamine® 2441 (modified polyamine), and reaction products of monoethanolamine or other mono-primary or di-secondary amines with epoxides.

[0027] To test the effectiveness of the decomposition promoters, multiple combinations of decomposition agents are added to polycarbonate and heated at 165°C. Only polycarbonate and activator are utilized as opposed to a formulated composition. Gas chromatography-mass spectrometry (GC-MS) techniques are used to determine the amount of carbon dioxide (CO2) liberated (see Figure 1 for results). The polycarbonate utilized is Lexan® 101R from Sabic. As can be seen in Figure 1, polycarbonate does not liberate CO2 when heated to 165°C without the use of a decomposition agent. However, when ethanolamine is added to polycarbonate and heated, the CO2 / O2 content is greater than 40% at 165°C.

[0028] In Figure 1, the CO2 amount is listed as the ratio of carbon dioxide or CO2 to oxygen or O2. Gas chromatography-mass spectrometry (GC-MS) is performed under standard atmospheric conditions and is used to normalize the CO2 amount so that differences in sample size or injection volume do not affect the results since O2 levels are stable under atmospheric conditions.

[0029] Figure 2 shows the chemical structures of some of the decomposition initiators listed in Figure 1. It can be seen that as the electron density increases and the steric hindrance decreases, the initiator tends to be more effective at lowering the decomposition temperature of polycarbonate to liberate CO2.

[0030] The result in Figure 1, labeled "20-4", is a fully formulated heat-activated foaming adhesive. Formulation 20-4 contains polycarbonate polymer along with an amine-containing ingredient used to polymerize the epoxy groups in the adhesive. Since the 20-4 formulation does not contain a typical blowing agent such as azodicarbonamide, it was not expected to foam. Therefore, it is presumed that the amine-containing compound can reduce the decomposition temperature of the polycarbonate polymer. Furthermore, it is determined that the two amine-containing compounds used in the 20-4 formulation to cure the epoxy resin, DDA 10 and Omicure® U-52M, were useful polycarbonate decomposers to release CO2. The results in Figure 1, labeled Lexan® 101R + Omicure® U-52M + DDA 10, show that the epoxy curing agent DDA 10 (dicyandiamide) and the accelerator for DDA 10, Omicure® U-52M (a substituted urea), cause similar amounts of CO2 / O2 release from the decomposition of polycarbonate polymer compared to the 20-4 formulation. Thus, it is surprising and useful to discover that not only are amine or nitrogen-containing compounds capable of decomposing polycarbonate well below its softening point releasing CO2, but also that two amine-containing raw materials commonly used to crosslink epoxy thermosets are particularly capable as polycarbonate decomposers.

[0031] As shown in FIG. 1 that compounds with urea functionality, preferably substituted ureas and dicyandiamide, both useful for crosslinking with epoxy adhesives, and each of these can decompose polycarbonate to release CO2, tests are performed to understand the effect of the concentration of amine-containing components relative to CO2 generation. Table 1 shows model formulations selected to help explore the effect of dicyandiamide and urea on the decomposition of polycarbonate polymers to release CO2. The model formulations use a 100% stoichiometric ratio of reactive hydrogen to epoxy groups. In this case, stoichiometry (or stoichiometric ratio) refers to the ratio of hardener (DDA 50) to epoxide functionality required to react with all epoxide functionality present. When 100% stoichiometry is shown, it means that enough hardener is present to crosslink with 100% of the epoxy groups. Similarly, if an 80% stoichiometry is stated, this means that there is enough hardener to consume 80% of the epoxy groups (20% of the epoxide rings remain unreacted or become homopolymer), etc.

[0032] [Table 1]

[0033] Based on the model formulations in Table 1, tests are performed using different stoichiometric ratios of dicyandiamide to epoxy-containing raw materials in the formulations. The ratios of polycarbonate dissolves (PcD) from those formulations based on the model formulations and dicyandiamide are then tested using GC-MS for CO2 evolution using varying stoichiometric ratios of hardeners. Only dicyandiamide is used as the decomposition accelerator in Table 2 below. In Table 3, both dicyandiamide and urea were used. The ratio of polycarbonate to urea was held constant in Table 3 below.

[0034] As mentioned before, since it is usually not possible to incorporate polycarbonate into the formulation due to its high softening point, a melt is made by dissolving the polycarbonate in a suitable solvent. In this case, liquid epoxy is used as the solvent that later becomes part of the curing composition. It is therefore a reactive solvent. In this example, the melt consists of 45% by weight of polycarbonate dissolved in 55% by weight of bisphenol F-based epoxy resin, but other ratios can be considered. In the temperature range of 140°C to 250°C, the melt containing the polycarbonate and epoxy mixture does not decompose by itself to release CO2. However, CO2 is generated by the addition of decomposition accelerators, especially effective amines or nitrogen-containing bases. The generated CO2 can be used to foam adhesives or sealants.

[0035] [Table 2]

[0036] [Table 3]

[0037] Table 2 above shows that the decomposition of polycarbonate polymer in the presence of dicyandiamide hardener releases CO2. Regardless of the stoichiometric ratio used in the model formulation, the amount of CO2 released is relatively small, ranging from a ratio of about 0.03 to 0.60 depending on the temperature used for decomposition and the stoichiometric ratio used. Increasing the test temperature increases the amount of CO2 produced.

[0038] Table 3 above shows the CO2 release with the presence of dicyandiamide hardener in combination with urea accelerator. The amount of CO2 generation with the addition of urea is significantly greater than with dicyandiamide alone. The amount of CO2 generated with both dicyandiamide and urea present ranges from a ratio of about 0.70 to 3.3 depending on the test temperature and stoichiometric ratio. The amount of CO2 generation increased as the test temperature increased. The columns in Tables 2 and 3 labeled 0% do not include an amine-containing hardener compound to assist in decomposing the polycarbonate polymer. In the absence of an amine-containing compound, the amount of CO2 generation is very low, indicating that dicyandiamide and urea in combination can act as a decomposition initiator for polycarbonate polymers. Table 3 shows that the use of urea and dicyandiamide together is more effective at decomposing polycarbonate and releasing CO2 gas than the use of dicyandiamide alone.

[0039] Tables 4 and 5 show the CO2 liberated when L-TE01-35E and L-TE01-30A are used as polycarbonate decomposition accelerators. L-TE01-35E is a polymer produced from the reaction of a diepoxide with monoethanolamine, with excess epoxy to provide epoxy termination. L-TE01-30A is a reaction product of a diepoxide with monoethanolamine, with excess amine to provide amine termination. These are generally thermoplastic compositions that can be useful in formulated heat-activated materials capable of structural bonding and reinforcement. Among other things, these thermoplastic materials can increase the fracture strain and peel strength of structural foam materials. There are tertiary amines along the backbone of the reaction product. It is presumed that these amines reduce the decomposition temperature of the polycarbonate, thereby facilitating CO2 generation. The results in Tables 4 and 5 show that for each polymer, there is CO2 generated from the polycarbonate melt. Recall that in this case, the polycarbonate melt (PcD) consists of 45% by weight polycarbonate polymer dissolved in 55% by weight bisphenol A (or optionally bisphenol F) liquid epoxy. As the concentration of L-TE01-35E increases relative to PcD, the amount of CO2 production reaches a maximum ratio of 7.4 at a composition of 67 / 33L-TE01-35E / PcD. This is probably due to the fact that for higher relative ratios of TE01-35E and PcD, the percentage of polycarbonate decreases to the point where there is not enough polycarbonate to decompose, thereby resulting in a lower total gas production. A similar phenomenon is observed when amine-terminated products are used. As the concentration of L-TE01-30A increases relative to PcD, the amount of CO2 production reaches a maximum ratio of 6.7 at a composition of 67 / 33L-TE01-35E / PcD. However, there may be limits to the usefulness of the concentrations of either L-TE01-35E or L-TE01-30A in an adhesive formulation.

[0040] [Table 4]

[0041] [Table 5]

[0042] Table 6 shows additional polycarbonate decomposers based on metal salts and complexes, amine derivatives, blocked isocyanates or silicates. Two polycarbonate decomposers that are particularly useful as one-component heat-activated adhesives shown in Table 6 are Curezol® 2 MAOK and Ancamine® 2441. These are epoxy hardeners that can produce shelf-stable adhesives. When Curezol® 2 MAOK is mixed with polycarbonate melt (PcD), a CO2 / O2 gas ratio of about 3.4 is liberated at 177°C (350°F). When Ancamine® 2441 is mixed with polycarbonate melt, a CO2 / O2 gas ratio of about 2.2 is liberated. These compare favorably with dicyandiamide, which releases about 0.3 when tested under comparable conditions.

[0043] [Table 6] TIFF2024541428000008.tif151141

[0044] The polycarbonate used as the basis for the present invention is a bisphenol A-based polycarbonate with a melt index of 10 g / 10 min (measured according to ASTM D1238) when measured at 300° C. and 1.2 kg weight. However, it is contemplated that polycarbonate polymers with lower or higher melt indexes may also be used. The polycarbonate used in the above experiments is obtained directly from a polymer manufacturer. However, recycled polycarbonate can be used to generate CO2 to provide foaming as well. It is also possible that other carbonate monomers or polymers can be used for carbon dioxide release. Propylene carbonate, ethylene carbonate, poly(alkylene carbonate) and other organic carbonates can be used for CO2 release for foaming.

[0045] As previously indicated, due to the high softening or melting point of polycarbonate, it is usually not possible to blend it with other ingredients in a heat-activated product without activating the compounded product during compounding. It is therefore necessary to lower the softening point of polycarbonate. Liquid epoxy can be used as a solvent to dissolve the polycarbonate, thereby creating a melt product. Solid epoxy can be used as well, but it may be a less effective solvent. This melt product can then be introduced with other ingredients to create a foamed thermoset adhesive.

[0046] Improved results are obtained when using bisphenol F epoxy because the solvent is less viscous than typical bisphenol A epoxy, thereby providing faster solubilization and potentially higher solute concentration. 36.85% bisphenol F epoxy (Kukdo® YDF-170) is heated to 191° C. in a stirred reactor using a Cowles blade. Over a period of 75 minutes, 30.15% polycarbonate (Entec® P1010L1) is added to the stirred reactor. After all of the polycarbonate is added, the blend is mixed for an additional hour to dissolve all of the polycarbonate. Finally, 33.00% solids epoxy (DER 667) is added over a period of 20 minutes. This was an optional step since DER 667 is not always utilized in the melt, however, a 45:55 polycarbonate:bisphenol F liquid epoxy weight ratio was maintained throughout the run. The melt is then removed from the reactor, cooled, and reduced in size to granules or powder. Although a solid material is produced for these experiments, the material may be semi-solid or liquid, depending on the desired physical state defined by the relative percentages of solvent and solute to incorporate via formulation. Upon cooling, the physical state is controlled by the relative ratios of solvent / solute. Solid epoxy additions may be added for the purpose of making a solid melt product that does not aggregate at room temperature or at slightly elevated temperatures such as 40°C.

[0047] The above solution product is then incorporated with additional ingredients to develop a heat-activated foaming epoxy adhesive. Table 7 below shows sample formulations as foaming thermosetting epoxy adhesives that contain a typical chemical foaming agent such as azodicarbonamide, a newly developed polycarbonate solution, and a combination of two chemical foaming ingredients.

[0048] [Table 7]

[0049] Table 8 shows the base properties of each formulated material from Table 7. As the results show, it is possible to formulate adhesives using polycarbonate as the sole foaming ingredient. The current foaming agent, azodicarbonamide, has an amine group in the molecule: [ka]

[0050] It is believed that these amine groups, especially the four active hydrogens (including two primary), can reduce the latency of the formulated epoxy adhesive; i.e., the formulated material has a reduced shelf life before heat activation. The use of polycarbonate as a blowing agent can produce a more latent formulated product. Such evidence is shown in Table 8 below. Compared to the expansion of materials held at 23°C, the retention of volumetric expansion of materials exposed to high temperatures (43°C to 54°C) is greater for compositions containing more polycarbonate and less azodicarbonamide. The temperatures of 43°C and 54°C were chosen as representative temperatures that may be encountered during shipping and / or storage in warm climates.

[0051] [Table 8]

[0052] The fact that volume expansion retention decreases for materials containing more azodicarbonamide supports the premise that the amine groups reduce the adhesive's latency and are a significant source of shelf life degradation. The amine groups can react with the epoxy, raising the molecular weight and thereby increasing the adhesive's viscosity, resulting in less expansion with the same amount of gas evolution, but at the same time reducing the composition's ability to develop adhesion to the substrate. Note that the foam percentage reduction effect is usually more evident at higher aging temperatures (54°C as shown in Table 8).

[0053] Tables 9-10 show sample formulations and corresponding volume expansion and lap shear results. The results show that it is possible to obtain good foaming and lap shear strength using polycarbonate as the foaming agent over a range of cure temperatures and times. The adhesive foams well and has good lap shear performance even at cure temperatures as low as 120°C.

[0054] [Table 9]

[0055] [Table 10]

[0056] For the experimental results shown in Tables 8 and 10, the tests proceed as follows: Volume expansion and uncured / cured density are measured utilizing metal specimens measuring 25 x 100 x 0.75 mm (cold rolled steel). The uncured sample size is 12.7 x 63.5 x 2.7 mm. The cure schedule is 163°C (325°F) for 30 minutes. Lap shear strength (ASTM D1002) is measured utilizing metal specimens (EG-60 coated) measuring 25 x 100 x 1.5 mm. The uncured sample size is 25 x 25 x 2.75 mm with a 3 mm bond line and 25 mm overlap. The cure schedule is 163°C (325°F) for 30 minutes and the test speed is 50.8 mm (2.00 in) / min. T-peel is measured utilizing metal specimens (EG-60 coated) with dimensions of 25 x 100 x 0.75 mm. The specimens are bent at a 90 degree angle at 25 mm leaving 25 mm for the gripping area and 75 mm for the material bond area. The uncured sample size is 25 x 75 x 1.50 mm with a 1.5 mm (glass bead) bond line. The cure schedule is 163°C (325°F) for 30 minutes and the test speed is 254 mm / min. Tensile strength and tensile break strain (ASTM D638) are measured using a 3 mm cured sample thickness and a JIS 6301-1 dogbone sample size / geometry. The cure schedule is 163°C (325°F) for 30 minutes and the test utilizes a 50 mm extensometer at 5.0 mm / min. Glass transition temperature is measured utilizing ASTM D7028-07.

[0057] The teachings described therein show that polycarbonate thermoplastics can be decomposed well before their decomposition temperature by the use of decomposers, particularly amines, that generate carbon dioxide, which are used as chemical blowing agents. Also described is the development of a melt using epoxy as a solvent to dissolve polycarbonate in order to lower its softening point so that it can be easily blended with other ingredients used in the heat-activated material. Ultimately, what is described is the use of polycarbonate within the melt as an ingredient in an epoxy adhesive formulation to produce a material that has good mechanical performance and can be foamed.

[0058] The polycarbonates described herein may be utilized in a variety of formulations, which may include epoxy-based materials and may also include additional components, including tougheners, flexibilizers, curing agents, accelerators, various reinforcing components, and other additives.

[0059] It is possible that the formulations described herein include at least one type of polymer particles. As used herein, the term "polymer particles" as well as any other raw material of the present teachings can include one or more types of polymer particles. Various types of polymer particles can be used in the practice of the present teachings, and often include one or more elastomers. In general, the polymer particles are preferably at least 4% by weight, more typically at least 7% by weight, even more typically at least 10% by weight, even more typically at least 13% by weight, even more typically at least 16% by weight of the formulation, and the polymer particles are preferably less than 90% by weight, more typically less than 40% by weight, even more typically less than 30% by weight of the formulation, although in certain embodiments, more or less amounts may be used.

[0060] The polymer particles may include one or more core / shell polymers that may be pre-dispersed in the epoxy. The process for forming the core-shell material in the liquid epoxy avoids the agglomeration of the core-shell particles that is common in the case of "dry" core-shell polymer particles (e.g., agglomeration may occur during the drying process). Examples of products made by this process may be described in one or more of U.S. Pat. Nos. 3,984,497; 4,096,202; 4,034,013; 3,944,631; 4,306,040; 4,495,324; 4,304,709 and 4,536,436. The polymer particles may be formed by an emulsion polymerization process. This process may include adding a solvent with the resin. As a result of the incompatibility between the resin / solvent and water, the water settles out of the material as the core-shell particles move into the resin, resulting in reduced agglomeration. Alternatively, high speed dispersion can be effective in deagglomerating the core / shell material. However, surfactants may remain after spray drying or solidification of the core / shell material. This residual surfactant may be detrimental to the material's resistance to environmental exposure conditions involving water, such as salt spray and humidity. Materials that are not exposed to environmental exposure conditions typically show no difference between dry and liquid core / shell masterbatches, assuming there is sufficient deagglomeration of the dry material.

[0061] Examples of useful core-shell graft copolymers may be those in which a hard-containing compound such as styrene, acrylonitrile, or methyl methacrylate is grafted to a core made from a polymer of a soft or elastomeric compound such as butadiene or butyl acrylate. U.S. Pat. No. 3,985,703 describes useful core-shell polymers in which the core is made from butyl acrylate, but can also be based on ethyl isobutyl acrylate, 2-ethylhexyl acrylate, or other alkyl acrylates, or mixtures thereof. The shell portion may be polymerized from methyl acrylates such as methyl methacrylate, and optionally other alkyl acrylates and alkyl methacrylates, such as ethyl, butyl, or mixed acrylates or methacrylates, since these materials are compatible with the phenoxy resin and any epoxy resins used in the formulation. Up to 40 weight percent or more of the shell monomers may be styrene, vinyl acetate, vinyl chloride, and the like. Examples of core-shell graft copolymers include, but are not limited to, "MBS" (methacrylate-butadiene-styrene) polymers made by polymerizing methyl methacrylate in the presence of polybutadiene or polybutadiene copolymer rubber.

[0062] Examples of useful core / shell polymers include, but are not limited to, those sold under the trademark Kane Ace® available from Kaneka. Particularly preferred grades of Kane Ace® core / shell are sold under the names MX-257 and M711 or Clear Strength® E-950 available from Arkema. The core / shell polymer may be from about 5% to about 30% by weight of the formulation.

[0063] The formulation may include a flexibilizing agent. The use of the term flexibilizing agent may relate to a single flexibilizing agent or to a combination of different flexibilizing agents. Although other flexibilizing agents may be used, preferred flexibilizing agents include amine-modified, epoxy-modified or both polymers. These polymers may include thermoplastics, thermosettables, elastomers, combinations thereof, and the like. These polymers may be modified with aromatic or non-aromatic epoxies and / or modified with bisphenol-F type, bisphenol-A type, combinations thereof, or other types of epoxies. Examples of preferred flexibilizing agents are the epoxidized polysulfides sold under the trademarks EPS-350 and EPS-80 available from Akzo Nobel.

[0064] Phenol-containing molecules such as the flexibilizer Rez-Cure® EP1820 (available from Innovative Resin Systems) are one possible material that can be utilized. Another preferred example of a flexibilizer is an epoxy-dimer acid elastomer sold under the trademark HYPOX® DA 323, available from Huntsman. Other preferred examples of flexibilizers are polyurethane-modified epoxies sold under the trademarks GME-3210 and GME-3220, available from GNS Technologies. From experimental results, it has been observed that polyurethane-modified epoxy flexibilizers improve impact strength (especially as demonstrated by wedge impact testing) while at the same time minimizing the effect on lowering the glass transition temperature. Yet further examples of preferred flexibilizers are amine- or epoxy-terminated polyethers, such as JEFFAMINE® D-2000, available from Huntsman, and DER 732, available from Dow Chemical Company. Flexibility agents based on cashew nut shell liquids, such as epoxidized liquid Cardolite® NC-514 and Cardolite Lite® 2513 HP, are also useful flexibilizers. Any of the individual flexibilizers discussed herein may be used separately or in combination with one another in the formulations of the present invention, unless otherwise specified.

[0065] The formulation may include a phenoxy resin component. Phenoxy resins are high molecular weight thermoplastic condensation products of bisphenol A with epichlorohydrin and its derivatives. Examples of suitable materials are PKHB, PKHC, PKHH, PKHJ, PKHP pellets and powders. Alternatively, phenoxy / polyester hybrids and epoxy / phenoxy hybrids may be used.

[0066] The formulation may include one or more additional polymers or copolymers, which may include a variety of different polymers, such as thermoplastics, elastomers, plastomers, combinations thereof, etc. For example, but not limited to, polymers that may be suitably incorporated include halogenated polymers, polycarbonates, polyketones, urethanes, polyesters, silanes, sulfones, allyls, olefins, styrenes, silicones, phenolics, rubbers, polyphenylene oxides, terephthalates, acetates (e.g., EVA), acrylates, methacrylates (e.g., ethylene methyl acrylate polymers), or mixtures thereof. Other possible polymeric materials may be or include, but are not limited to, polyolefins (e.g., polyethylene, polypropylene), polystyrene, polyacrylates, poly(ethylene oxide), poly(ethyleneimine), polyesters, polyurethanes, polysiloxanes, polyethers, polyphosphazines, polyamides, polyimides, polyisobutylene, polyacrylonitrile, poly(vinyl chloride), poly(methyl methacrylate), poly(vinyl acetate), poly(vinylidene chloride), polytetrafluoroethylene, polyisoprene, polyacrylamide, polyacrylic acid, polymethacrylates.

[0067] One or more curing agents and / or curing agent accelerators may be added to the formulation. The amount of curing agent and curing agent accelerator may vary widely within the formulation depending on the desired type of cell structure, the desired amount of expansion of the formulation, the desired rate of expansion, the desired structural properties of the formulation, etc. Exemplary ranges of curing agents or curing agent accelerators present in the formulation range from about 0.001% to about 7% by weight.

[0068] The formulation may also include one or more reinforcing components. Preferably, the reinforcing components include materials that are generally non-reactive with other components present in the formulation. It is contemplated that the reinforcing components may also impart properties such as strength and impact resistance to the formulation.

[0069] Examples of reinforcing components include wollastonite, silica, diatomaceous earth, glass, clay (including, for example, nanoclay), glass beads or glass spheres, glass, carbon or ceramic fibers, nylon fibers, aramid fibers, or polyamide fibers. The one or more reinforcing components may be selected from mineral reinforcing materials such as diatomaceous earth, clay (including, for example, nanoclay), pyrophyllite, sauconite, saponite, nontronite, wollastonite, or montmorillonite. The reinforcing component may include silica and / or calcium mineral reinforcing materials. The reinforcing component may include glass, glass beads or glass spheres, carbon or ceramic fibers, nylon fibers, aramid fibers, or polyamide fibers (e.g., Kevlar®). The reinforcing component may be wollastonite. The reinforcing component may be fibers having an aspect ratio of about 20:1 to about 3:1. The reinforcing component may be fibers having an aspect ratio of about 15:1 to about 10:1. The reinforcing component may be fibers having an aspect ratio of about 12:1. The reinforcing component can improve a first physical property while substantially avoiding any significant detrimental effect on a second physical property. As one example, the selected reinforcing component can improve the overall modulus of the material while minimizing detrimental effects on the failure strain. The material may further include one or more fillers including pigments or colorants, calcium carbonate, talc, silicate minerals, vermiculite, mica, and the like.

[0070] The reinforcing component in the formulation, if used, can range from 10% or less to 90% or more by weight of the formulation, but more typically ranges from about 20% to about 55% by weight of the formulation. According to some embodiments, the formulation may include from about 0% to about 30% by weight of the reinforcing component, more preferably just under 10% by weight.

[0071] Other additives, agents or performance modifiers may also be included in the formulation if desired, including, but not limited to, UV resistant agents, flame retardants, polymer particles, heat stabilizers, colorants, processing aids, lubricants, and the like.

[0072] As used herein, unless otherwise expressly stated, the teachings contemplate that any member of a genus (list) may be excluded from the genus and / or any member of a Markush grouping may be excluded from the grouping.

[0073] Unless otherwise expressly stated, any numerical value described herein includes all values ​​from the lower value to the upper value in increments of one unit, provided that there is a separation of at least two units between any lower value and any upper value. As an example, if an amount, property, or value of a process variable, such as temperature, pressure, time, etc., is stated to be, for example, 1 to 90, preferably 20 to 80, more preferably 30 to 70, it is intended that intermediate range values ​​(e.g., 15 to 85, 22 to 68, 43 to 51, 30 to 32, etc.) are within the scope of the teachings herein. Similarly, individual intermediate values ​​are also within the scope of the teachings. For values ​​less than one, one unit is considered to be 0.0001, 0.001, 0.01, or 0.1 accordingly. These are merely examples of what is specifically intended, and all possible combinations of numerical values ​​between the lowest and highest values ​​listed are considered to be expressly set forth within the application in a similar manner. As can be seen, teachings of amounts expressed herein as "parts by weight" also contemplate the same ranges being expressed in terms of weight percent. Thus, expression of a range in terms of "at least 'x' parts by weight of the resulting composition" also contemplates teaching a range in weight percent of the resulting composition for the same recited amount "x."

[0074] Unless otherwise expressly stated, all ranges include both endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30," including at least the specified endpoints. Unless otherwise expressly stated, teachings using the term "about" or "approximately" in combination with a numerical quantity include teachings of the recited amount as well as approximations of the recited amount. For example, a teaching of "about 100" includes the teaching of "100."

[0075] The disclosures of all articles and references, including patent applications and published patents, are incorporated by reference for all purposes. The term "consisting essentially of" to describe a combination is intended to include the identified elements, ingredients, components, or steps, as well as such other elements, ingredients, components, or steps that do not materially affect the basic and novel properties of the combination. The use of the terms "comprising" or "including" to describe a combination of elements, ingredients, components, or steps herein also contemplates embodiments that consist of or consist essentially of the elements, ingredients, components, or steps in question.

[0076] Multiple elements, ingredients, components or steps may be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step may be divided into separate multiple elements, ingredients, components or steps. The disclosure of "a" or "one" to describe an element, ingredient, component or step is not intended to exclude additional elements, ingredients, components or steps.

[0077] It is understood that the above description is illustrative and not limiting. Many embodiments and many applications other than the examples provided will become apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present invention should not be determined with reference to the above description, but instead with reference to the appended claims and the full scope of equivalents to which such claims are entitled. The disclosures of all papers and references, including patent applications and published patents, are incorporated by reference for all purposes. The omission of any aspect of the subject matter disclosed herein in the appended claims should not be interpreted as a disclaimer of such subject matter or as the inventors not accepting such subject matter as part of the subject matter of the disclosed invention.

Claims

1. In the method, combining a polycarbonate thermoplastic with a decomposition initiator to decompose the polycarbonate; heating the polycarbonate thermoplastic and the decomposition initiator to a temperature between 120°C and 250°C to release carbon dioxide; The method of claim 1, wherein the polycarbonate thermoplastic and the decomposition initiator are combined with one or more additional ingredients to form a heat-activated material that foams as a result of the release of carbon dioxide.

2. 10. The method of claim 1, wherein the decomposition initiator comprises an amine, preferably selected from tertiary amines, imidazoles, amine adducts, triazoles, and ammonium derivatives.

3. 3. The method of claim 1 or 2, wherein the decomposition initiator comprises dicyandiamide or a compound having a urea functionality, preferably a substituted urea.

4. 3. The method of claim 1 or 2, wherein the decomposition initiator comprises the reaction product of bisphenol A epoxy and monoethanolamine.

5. 3. The method of claim 1 or 2, wherein the decomposition initiator comprises a material selected from metal carbonates, blocked isocyanates, and ammonium salts, metal halides, metal hydroxides, metal triflates, metal stearates, organophilic phyllosilicates, metal acetylacetonates, titanate complexes, metal phosphate esters, Lewis acids, or any combination thereof.

6. 3. The method of claim 1 or 2, wherein the polycarbonate thermoplastic is dissolved in a suitable solvent to form a dissolved product.

7. The method of claim 6 , wherein the solvent comprises a liquid epoxy, a solid epoxy, or a combination of a liquid epoxy and a solid epoxy.

8. The method of claim 6 , wherein the solvent comprises a polycarbonate polyol or a polycaprolactone polyol.

9. 7. The method of claim 6, wherein the solvent comprises an organic solvent including, but not limited to, acetone, methyl ethyl ketone, diethyl ketone, toluene, or xylene.

Images