Laser-weldable polyester compositions, their preparation and processing, and uses

Abstract

The present invention relates to a laser-weldable polyester composition, and more particularly to a laser-weldable fiber-reinforced polybutylene terephthalate composition comprising (A) polybutylene terephthalate resin (PBT), (B) glass fiber, and (C) an alkali metal salt of a fatty acid having 24 to 40 carbon atoms, wherein component (B) is present in an amount ranging from 15 to 100 parts by mass, based on 100 parts by mass of component (A), and component (C) is present in an amount ranging from 1.75 to 4.5 parts by mass, based on 100 parts by mass of component (A). The present invention also relates to methods for preparing the laser-weldable fiber reinforced polyester composition, methods for making molded parts from the laser-weldable fiber reinforced polyester composition, laser-transparent molded parts made from the laser-weldable fiber reinforced polyester composition, methods for laser welding laser-transparent molded parts made from the laser-weldable fiber reinforced polyester composition onto a laser light absorbing polymer substrate, and composite articles comprising a molded article made from the laser-weldable fiber reinforced polyester composition joined by laser welding onto a laser light absorbing polymer substrate.

Description

[Technical Field]

[0001] The present invention relates to a laser-weldable polyester composition, and more particularly to a laser-weldable fiber-reinforced polyester composition comprising polybutylene terephthalate resin and glass fibers. - a method for preparing a laser-weldable fiber-reinforced polyester composition; - a method for producing molded parts from laser-weldable fiber-reinforced polyester compositions; - laser-transparent molded parts made from laser-weldable fiber-reinforced polyester compositions; - a method for laser welding a laser-transparent molded part made from a laser-weldable fiber-reinforced polyester composition onto a laser-light-absorbing polymer substrate; and - a composite article comprising a molded article made from a laser-weldable fiber-reinforced polyester composition joined by laser welding onto a laser-light-absorbing polymer substrate. Also relates to. [Background technology]

[0002] There are various processes for welding plastic moldings, such as hot tool welding, vibration welding, and laser welding. Laser transmission welding is an alternative to vibration welding and hot tool welding, and has recently seen an ever-increasing use, especially with the use of diode lasers. Laser-weldable polyester compositions are known from the prior art and are described in various patents and patent applications.

[0003] U.S. Patent Application Publication No. 2008 / 153957 describes a laser-weldable polyester composition. The composition of U.S. Patent Application Publication No. 2008 / 153957 includes (A) a polybutylene terephthalate (PBT) resin and (B) a fatty acid compound in an amount ranging from 0.01 to 1.0 pbw, preferably about 0.03 to 0.5 pbw, based on 100 parts by weight (pbw) of the PBT resin. The fatty acid compound is preferably a fatty acid ester, a fatty acid amide, or a metal salt of a C12-36 fatty acid. Metal salts of C12-36 fatty acids can include, for example, alkali metal salts (e.g., sodium salts and potassium salts), alkaline earth metal salts (e.g., magnesium salts and calcium salts), salts of metals from Group 2B of the Periodic Table of Elements (e.g., zinc salts), and salts of metals from Group 3B of the Periodic Table of Elements (e.g., aluminum salts), either alone or in combination. According to US Patent Application Publication No. 2008 / 153957, adding a fatty acid-based compound to a resin composition at the above-mentioned specific low ratio effectively ensures an improvement in laser transmittance, but a lower ratio of the fatty acid-based compound may not sufficiently improve laser transmittance, while a higher ratio of the fatty acid-based compound may decrease laser transmittance. The composition of US Patent Application Publication No. 2008 / 153957 may contain additional components such as fibers and fillers and other auxiliary additives for PBT-based polyester compositions. The additional component in the composition of US Patent Application Publication No. 2008 / 153957, listed as optional component (C), was a cyclic polyester oligomer. However, in the examples of US Patent Application Publication No. 2008 / 153957, component (B) showed a moderate effect on transmittance and weld strength, while component (C) showed a slight additional effect on transmittance but a much more pronounced effect on weld strength.

[0004] U.S. Patent Application Publication No. 2011 / 288220 describes a composition for laser-transparent molded articles, comprising (A) a polyester and (B) sodium or potassium carbonate or bicarbonate. The composition may also include (C) additional additives. Component (B) is present in an amount ranging from 0.05 to 2.0 wt %, based on the total weight of the composition, and is added to improve laser light transmittance. Additional additives include reinforcing fibers, lubricants, and mold release agents. Potential lubricants and mold release agents include long-chain fatty acids and their salts. As noted in U.S. Patent Application Publication No. 2011 / 288220, these may be used in amounts up to 1 wt %. U.S. Patent Application Publication No. 2011 / 288220 provides a series of composition examples containing PBT and varying amounts of the component (B) additive without glass fiber, and a series of composition examples containing PBT, varying amounts of the component (B) additive, and 30 wt% glass fiber. Both series demonstrated optimal laser light transmittance with respect to the amount of component (B). The first series exhibited the highest laser light transmittance at amounts ranging from 0.4 to 0.5 wt% of component (B), while the second series exhibited the highest laser light transmittance at amounts ranging from 0.3 to 0.4 wt% of component (B). These mass percentages correspond to 0.40 to 0.50 pbw of component (B) based on 100 pbw of PBT resin for the first series, and 0.42 to 0.57 pbw of component (B) based on 100 pbw of PBT resin for the second series. Furthermore, for all compositions corresponding to equivalent amounts of component (B), the laser light transmittance of the glass fiber reinforced compositions was lower than that of the unreinforced compositions.

[0005] U.S. Patent Application Publication No. 2012 / 231285 describes the use of a thermoplastic molding composition for producing laser-transparent molded articles, the composition comprising (A) a polyester, (B) an alkali metal salt of an aliphatic carboxylic acid, and optional (C) further additives. The amount of the alkali metal salt (B) is 0.2 to 2% by weight based on 100% by weight of (A) and (B). The composition may contain up to 70% by weight of the further additives. Preferred alkali metals in the alkali metal salt of component (B) are potassium and / or sodium. Furthermore, preference is given to saturated or unsaturated carboxylic acids having 1 to 40, more preferably 1 to 22, carbon atoms. Several examples of compositions based on PBT as component (A) and varying amounts of either sodium acetate or sodium stearate as component (B) are shown. Increasing the amount of alkali metal salt of aliphatic carboxylic acid (B) up to a level of about 0.8-1.0 wt% for both sodium acetate and sodium stearate significantly increases laser light transmittance, but above this amount the increase in laser light transmittance plateaus or even decreases. Meanwhile, tensile strength remains nearly constant up to a level of about 0.8-1.0 wt%, but above that amount the tensile strength decreases. Furthermore, even with small additions of either sodium acetate or sodium stearate, the tensile strain at break decreases sharply, and further decreases consistently with increasing amounts for both sodium acetate and sodium stearate.

[0006] Overall, there is a need for laser-weldable compositions, particularly laser-weldable polyester compositions, that have high laser light transmittance and good weldability, as well as good mechanical properties, particularly tensile strength, elongation at break, and impact resistance. While mechanical properties can be improved by adding reinforcing agents, such components reduce laser light transmittance. Meanwhile, the addition of additives that improve laser light transmittance not only has its own limited effect on laser light transmittance, but also has an undesirable adverse effect on the mechanical properties of PBT-based polyester compositions. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2008 / 153957 [Patent Document 2] US Patent Application Publication No. 2011 / 288220 [Patent Document 3] US Patent Application Publication No. 2012 / 231285 [Patent Document 4] US Patent Application Publication No. 2010 / 0227182 [Patent Document 5] European Patent Application No. 1240243 [Patent Document 6] European Patent No. 1048439 [Non-patent literature]

[0008] [Non-Patent Document 1] ISO 307 [Non-patent document 2] TMG3 User Manual Version 3.0 [Non-patent document 3] ISO 7724-1-2-3 [Non-patent document 4] Plastverarbeiter 46 (1995) 9, 42~46 [Non-Patent Document 5] Kunststoffe 87, (1997) 3, 348~350 [Non-patent document 6] Kunststoffe 87 (1997) 11, 1632~1640 [Non-Patent Document 7] Kunststoffe 88, (1998), 2, 210~212 [Non-patent document 8] Plastverarbeiter 50 (1999) 4, 18~19 [Non-Patent Document 9] ISO 11357 [Non-Patent Document 10] ISO 1133 [Non-Patent Document 11] ISO 527-1A [Non-Patent Document 12] ISO 179 / 1eU [Non-Patent Document 13] ISO 527-1A(2019) Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, an object of the present invention is to provide a laser-weldable polyester composition, more particularly a laser-weldable fiber-reinforced polyester composition, which has an improved balance between laser light transmittance and mechanical properties, and preferably has both good laser light transmittance and good mechanical properties. [Means for solving the problem]

[0010] This object has been achieved by a fiber-reinforced polyester composition according to the present invention, which comprises (A) polybutylene terephthalate resin (PBT), (B) glass fiber, and (C) an alkali metal salt of a fatty acid having 24 to 40 carbon atoms. The glass fiber (component (B)) is present herein in an amount ranging from 15 to 100 parts by weight, based on 100 parts by weight of PBT (component (A)). The alkali metal salt of a fatty acid having 24 to 40 carbon atoms (component (C)) is present herein in an amount ranging from 1.75 to 4.50 parts by weight, based on 100 parts by weight of component (A).

[0011] The effect of the compositions according to the present invention containing the aforementioned amount of component (C) is a significant improvement in laser light transmittance, enabling a significant reduction in laser welding cycle time, while maintaining excellent mechanical properties. More specifically, the laser light transmittance increases more than would be expected based on a 1 pbw increase in component (C), while the mechanical properties, more specifically tensile strength, elongation at break, and / or unnotched impact properties, are lower than those of corresponding compositions without component (C), although the decrease is much smaller than that of corresponding compositions containing, for example, sodium stearate or sodium myristate instead of an equivalent amount of component (C). Furthermore, the laser light transmittance increases significantly more than when the corresponding metal salts of C24 to C40 fatty acids based on other metals, such as magnesium (a metal of the alkaline earth metal group) and aluminum (a metal of Group 3B of the Periodic Table of the Elements) are used. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graphical representation of the laser light transmittance measured at 980 nm and a thickness of 1.2 mm for compositions containing different amounts of sodium montanate (Examples EX-I to EX-V and Comparative Examples CE-A and CE-B). As can be seen, above 1 phr, there is a sharp increase in laser light transmittance up to about 2.5 phr, after which the level of laser light transmittance plateaus. [Figure 2] FIG. 1 is a graphical representation of tensile strength retention for different amounts of sodium montanate (C1), sodium stearate (C2) and sodium myristate (C3). [Figure 3] FIG. 1 is a graphical representation of the retention of elongation at break for different amounts of sodium montanate (C1), sodium stearate (C2), and sodium myristate (C3). [Figure 4] FIG. 1 is a graphical representation of the retention of unnotched impact resistance for different amounts of sodium montanate (C1), sodium stearate (C2) and sodium myristate (C3). DETAILED DESCRIPTION OF THE INVENTION

[0013] It should be noted that where a range having an upper and / or lower limit is recited, the range expressly includes not only the recited upper limit and the recited lower limit, but also any value within that range. For example, in "an amount in the range of 1.75 to 4.50 parts by weight," the range expressly includes 1.75 and 4.50, and any value between 1.75 and 4.50.

[0014] It should be noted that during the preparation of the composition of the present invention, in which components (A), (B), and (C) are mixed, for example, by melt mixing, some reaction may occur between the polybutylene terephthalate resin (PBT; component (A)) and the alkali metal salt of a fatty acid (component (C)). Thus, in the composition of the present invention, components (A) and (C) may exist as reaction products resulting from the reaction between component (A) and component (C). Possible reactions include, for example, transesterification and salt exchange.

[0015] In transesterification, the terephthalate carboxyl group and the fatty acid carboxyl group can be exchanged to result in a polyester chain having the fatty acid carboxyl group and the alkali metal salt of the carboxylic acid end group incorporated as the end group of the polyester chain, as represented by reaction (I). R PBT-1 -O-(O)C-C6H4-C(O)-OR PBT-2 +MO-(CO)-R FA → R PBT-1 -O-(O)CR FA +MO-(CO)-C6H4-C(O)-OR PBT-2 (I) In a salt exchange reaction, also called an ion exchange reaction, a proton (H) and a carboxylic acid group (R PBT The protonated carboxylic acid end groups in the polyester chain containing -C(O)-O) and alkali metal ions (M) and carboxyl groups (OC(O)-R FA ), resulting in the exchange of protons and alkali metal ions, as shown in reaction (II),FA and protonation of the polyester chains having alkali metal salts of the carboxylic acid end groups occurs. R PBT-3 -O-(O)C-C6H4-C(O)-OH+MO-C(O)-R FA → R PBT-3 -O-(O)C-C6H4-C(O)-OM+HO-C(O)-R FA (II) In the formula, R PBT-1 , R PBT-2 and R PBT-3 R represents a polyester chain having repeat units derived primarily from diacids and diols, more particularly from terephthalic acid and butanediol. FA represents the aliphatic chain of the fatty acid. FA contains 23 to 39 carbon atoms, while the corresponding carboxyl functional fatty acid group O—(CO)—R FA contains 24 to 40 carbon atoms. MO-(CO)- represents an alkali salt of a carboxylic acid group. -C(O)-OH represents a protonated carboxylic acid group. -C6H4- represents the aromatic ring of a terephthalic acid group.

[0016] Thus, in the compositions according to the invention, component (A) and component (C) can be present as such, as their reaction products, or in combination, i.e., partially as such and partially in the form of their reaction products. In the invention described herein, when the amounts of component (A) and component (C) are expressed either in wt % or parts by mass, the amount of component (C) is determined based on the alkali metal ions (M; the moiety of component MO-(CO)-R in the formulation. FA (added by the addition of) and a C24 to C40 carboxylic acid functional fatty acid group O—(CO)—R FAand the amount of component (C), which is exclusive of any protonated and / or esterified groups attached thereto, and the amount of component (A) refers to the total amount of components in the polyester chain, excluding alkali metal ions or carboxyl-functional C24-C40 fatty acid groups therein. For clarity, in other words, the bolded parts in the following structures are included in the amount of component (A), and the underlined parts are included in the amount of component (C).

[0017] [ka]

[0018] The amount is determined by the amount of ingredients used in preparing the composition, and is based on the amount of hydrolysis, acidification, and solubility of the soluble ingredients. 1 H-NMR solution spectroscopy and HPLC or GC can be used to quantify the amount in a composition or injection molded part by techniques known to those skilled in the art.

[0019] An example of an alkali metal salt of a fatty acid having 24 to 40 carbon atoms is sodium montanate: MO-(CO)-C27H55, where M is sodium (Na; molar mass = 22.99), and the carboxylic acid functional group is C28H55O2 (molar mass = 423.75 g / mol).

[0020] A polymer composition containing PBT and sodium montanate is known, for example, from U.S. Patent Application Publication No. 2010 / 0227182. This patent application describes a polyester composition containing PBT or another thermoplastic polyester and sodium montanate, which is typically unreinforced. The polyester composition has been used for bezel applications. Sodium montanate is used as a lubricant in an amount of 0.01 to 0.5 wt %, based on the total weight of the composition. U.S. Patent Application Publication No. 2010 / 0227182 focuses on low outgassing of bezels and does not mention the effects of sodium montanate on polymer welding behavior, laser light transparency, or the mechanical properties of molded parts made from the fiber-reinforced composition.

[0021] Component (A) in the composition according to the invention is a polybutylene terephthalate (PBT) resin. The PBT resin can be any thermoplastic polybutylene terephthalate resin suitable for use in fiber reinforced polymer compositions suitable for making fiber reinforced molded parts in a molding process and known in the art.

[0022] The polybutylene terephthalate resin is preferably a PBT homopolymer or PBT copolymer. PBT homopolymers consist primarily of copolymerized units of butylene and terephthalate. Such homopolymers can be preferably prepared by copolymerizing butanediol and terephthalic acid, with these monomers being used as the only monomers. PBT homopolymers may contain trace amounts of other components, such as trace impurities in butanediol and / or terephthalic acid, or other copolymerized units resulting from trace impurities formed during the polycondensation of butanediol and terephthalic acid. Preferably, PBT homopolymers consist of at least 99 mol% butylene and terephthalate units and at most 1 mol% other copolymerized units, based on the total molar amount of butylene, terephthalate, and other copolymerized units.

[0023] PBT copolymers may contain other comonomers, which may be copolymerized into the copolymer chain in small amounts. Examples of such other comonomers include difunctional monomers, i.e., monomers with two reactive sites, such as other diacids, e.g., isophthalic acid, other diols, e.g., ethylene glycol, and functional comonomers, e.g., 5-sodium sulfoisophthalate. Difunctional comonomers, if present, are preferably present in an amount up to about 10 mol %, or up to about 5 mol %. Comonomers with more than two reactive sites, such as trimellitic anhydride, trimellitic acid, pyromellitic dianhydride (pmda), and pentaerythritol, may preferably be incorporated as branching agents to increase melt viscosity. Such comonomers with more than two reactive sites are preferably present, if present, in an amount up to about 5 mol %, or even better, up to about 2.0 mol %. Preferably, the PBT copolymer contains at least about 85 mol% copolymerized units of butylene (butylene units) and terephthalate (terephthalate units) and up to about 15 mol% copolymerized units of an additional comonomer (comonomer units). Examples of additional comonomers that can be copolymerized into the PBT copolymer include isophthalic acid, propylene glycol, and butylene glycol. Preferably, the PBT copolymer contains at least about 90 mol%, more preferably at least about 95 mol%, and even more preferably at least about 98 mol% butylene units and terephthalate units, and correspondingly, preferably contains up to about 10 mol%, more preferably up to about 5 mol%, or even more preferably up to about 2.0 mol% comonomer units. In this specification, the mol percentages (mol%) of butylene units, terephthalate units, and comonomer units are all based on the total molar amount of the moles of butylene units, moles of terephthalate units, and moles of comonomer units in the copolymer.

[0024] In a preferred embodiment of the composition of the present invention, the PBT resin is a PBT homopolymer or a PBT copolymer containing at least 98 mol % copolymerized units of butylene and terephthalate and up to about 2.0 mol % copolymerized units of a comonomer, based on the total molar amount of the moles of butylene units, the moles of terephthalate units, and the moles of comonomer units in the copolymer.

[0025] The polybutylene terephthalate resin (A) used in preparing the composition according to the present invention can be any polybutylene terephthalate resin commonly used in preparing thermoplastic polyester molding compositions. The resin can have varying properties, such as viscosity and melt flow ratio. Suitably, the polybutylene terephthalate resin has a relative solution viscosity as high as about 2.8 or even higher, or as low as about 1.5 or even lower. Preferably, the PBT resin has an RSV in the range of 1.8 to 2.6, more preferably 2.0 to 2.5. As used herein, relative solution viscosity (RSV) is measured in m-cresol at a concentration of 1 g in 100 g of m-cresol at 25°C according to ISO 307.

[0026] The advantage of a PBT resin having a lower viscosity is that the laser-weldable fiber-reinforced polyester composition has improved processing behavior, and the advantage of a higher viscosity is that molded parts made from the composition have better mechanical properties. The advantage of a PBT resin having a viscosity in the preferred range is that the composition has both good processing behavior and good mechanical properties. The advantage of a PBT resin having a viscosity in the more preferred range is that the composition has a better balance of processing behavior and mechanical properties.

[0027] In a preferred embodiment, the PBT resin in the laser-weldable fiber-reinforced polyester composition has a relative solution viscosity (RSV) of 2.4 or less (based on experimental values). The advantage is that the welding process is improved, i.e., shorter cycle times are required for a given bond strength, or higher bond strengths are achieved with the same cycle time, compared to compositions containing a corresponding PBT resin with a higher viscosity.

[0028] Preferably, the laser-weldable fiber-reinforced polyester composition comprises component (A) in an amount ranging from 40 to 85 wt%, based on the total weight of the composition, which can be, for example, as low as 45 wt%, 50 wt%, 55 wt%, or 58 wt%, or as high as about 45 wt%, 50 wt%, 55 wt%, or 58 wt%, or as high as 80 wt%, 75 wt%, or 70 wt%, based on the total weight of the composition.

[0029] For the glass fibers of component (B), any glass fibers suitable for use in fiber-reinforced polyester compositions and molding processes for making fiber-reinforced molded parts from such compositions can be used. Suitable glass fibers are known in the art. The glass fibers for making the laser-weldable fiber-reinforced polyester compositions of the present invention can have lengths that vary over a wide range. They can be used in the form of roving or commercially available chopped glass. The glass fibers can be added as continuous fibers or as chopped or crushed glass fibers, allowing the fibers to be provided with a suitable sizing system and adhesion promoter or adhesion promoter system, such as those based on silanes. Particular preference is given here to glass fibers in the form of E-glass (an aluminoborosilicate glass with less than 1 wt. % alkali oxide, mainly used in glass-reinforced plastics). However, other types of glass fibers may also be used, such as A-glass (an alkali-lime glass with little or no boron oxide), E-CR-glass (an aluminoborosilicate glass with less than 1 wt. % alkali oxide, which has high acid resistance), C-glass (an alkali-lime glass with a high boron oxide content, e.g., used in short glass fibers), D-glass (a borosilicate glass with a high dielectric constant), R-glass (an aluminosilicate glass without MgO or CaO, which has high mechanical requirements), and S-glass (an aluminosilicate glass without CaO, with a high MgO content, and high tensile strength). The glass fibers preferably have a fiber diameter between 3 and 20 μm (micrometers). The glass fibers can have different cross-sections. Preferably, the glass fibers have a circular cross-section. These glass fibers can have a number-average diameter of, for example, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 12 μm, or about 15 μm. Preferably, the number-average diameter is in the range of 8 to 15 μm, more preferably in the range of 9 to 12 μm. The glass fibers can also have a non-circular cross-section, such as an oval cross-section or an elliptical-oval cross-section. A non-circular cross-section is herein characterized by a cross-section having different diameters in different directions.Suitably, the glass fibres having a non-circular cross section have a cross section with a maximum diameter of, for example, about 5 μm, or about 8 μm, or about 9 μm, or about 10 μm, or about 12 μm, or about 15 μm, or about 18 μm. Preferably, the number average value of the maximum diameter is in the range of 9 to 18 μm, more preferably in the range of 10 to 15 μm.

[0030] Component (B), i.e., glass fiber, is present in an amount ranging from 15 to 100 pbw, based on 100 pbw of component (A). Preferably, the amount of component (B) ranges from 25 to 80 pbw, more preferably from 30 to 70 pbw, and even more preferably from 35 to 60 pbw, based on 100 pbw of component (A). A higher minimum amount of component (B) has the advantage of providing the composition with better mechanical properties, more particularly, higher tensile strength. A lower maximum amount of component (B) has the advantage of providing the composition with better laser light transmittance.

[0031] One example of a composition according to the present invention is one that consists of 100 pbw of component (A), 100 pbw of component (B), and 2.0 pbw of component (C). Component (B) is present in an amount of 49.5 wt%, based on the total weight of the composition. Another example of a composition according to the present invention is one that consists of 100 pbw of component (A), 15 pbw of component (B), and 4 pbw of component (C). Component (B) is present in an amount of 12.6 wt%, based on the total weight of the composition. For compositions that include 100 pbw of component (A), 15 pbw of component (B), and 4 pbw of component (C), followed by one or more additional components, the weight percentage of component (B) can be less than 12.6 wt%, for example 10 wt%, based on the total weight of the composition. Preferably, the composition according to the present invention comprises component (B) in an amount ranging from 15 to 49.5 wt%, based on the total weight of the composition, which can be, for example, as low as 15 wt%, 20 wt%, or 25 wt%, or as high as about 15 wt%, 20 wt%, or 25 wt%, or as high as about 48 wt%, 44 wt%, or 40 wt%, based on the total weight of the composition.

[0032] The metal of the metal salt of component (C) is an alkali metal. The alkali metal is suitably lithium, sodium, or potassium, or a combination thereof. Preferably, the alkali metal is sodium, potassium, or a combination thereof, and more preferably, sodium.

[0033] The fatty acid in the fatty acid salt of component (C) is preferably a saturated fatty acid, an unsaturated fatty acid, or a combination thereof. The fatty acid may be a straight-chain fatty acid, a branched fatty acid, or a combination thereof. The fatty acid may contain heteroatoms, such as nitrogen atoms, or may not contain heteroatoms.

[0034] The saturated fatty acids that fall within the scope of the present invention and do not contain heteroatoms are represented by the formula C x H 2x O2, where x is an integer ranging from 24 to 40.

[0035] Preferably, the fatty acid is a straight chain saturated fatty acid containing no heteroatoms. Such a preferred straight chain saturated fatty acid containing no heteroatoms has the formula H3C(CH2) y It can be represented by CO2H, where y is an integer ranging from 22 to 38.

[0036] Examples of suitable straight chain saturated fatty acids are as follows: - Lignoceric acid (formula C 24 H 48 O2 or formula H3C(CH2) 22 represented by CO2H); - Pentacosylic acid, also known as pentacosanoic acid (formula C 25 H 50 O2 or formula H3C(CH2) 23 represented by CO2H); - Cerotic acid, also known as hexacosanoic acid (formula C 26 H 52 O2 or formula H3C(CH2) y24 represented by CO2H); Montanic acid, also known as n-octacosanoic acid (formula C 28 H56 O2 or formula H3C(CH2) 26 represented by CO2H); - Melissic acid, also known as triacontanoic acid (C 30 H 60 O2 or formula H3C(CH2) 28 represented by CO2H); - Raceroic acid, also known as dotriacontanoic acid (formula C 32 H 64 O2 or formula H3C(CH2) 30 represented by CO2H); - tetratrianioc acid (formula C 34 H 68 O2 or formula H3C(CH2) 32 represented by CO2H); - hexatrianioc acid (formula C 36 H 72 O2 or formula H3C(CH2) 34 CO2H); and - tetracontanioc acid (formula C 40 H 80 O2 or formula H3C(CH2) 38 (represented as CO2H).

[0037] In a preferred embodiment of the present invention, component (C) is a salt of a fatty acid having 26 to 36 carbon atoms (also referred to as a C26-C36 fatty acid), more preferably a salt of a fatty acid having 28 to 32 carbon atoms (also referred to as a C28-C32 fatty acid).

[0038] In a further preferred embodiment of the present invention, component (C) is a sodium or potassium salt of a C26 to C36 fatty acid, or a combination thereof. More preferably, component (C) is a sodium or potassium salt of a C28 to C32 fatty acid, or a combination thereof.

[0039] In a more preferred embodiment of the present invention, component (C) is a sodium or potassium salt of a linear saturated C26 to C36 fatty acid, examples of which include sodium montanate, potassium montanate, sodium triacontanoate, potassium triacontanoate, sodium dotriacontanoate, potassium dotriacontanoate, sodium hexatrianioate, potassium hexatrianioate, and any mixture thereof.

[0040] Component (C) is present in an amount ranging from 1.75 to 4.50 pbw, based on 100 parts by mass (pbw) of component (A). Suitably, the amount of component (C) is in the range of 1.9 to 4.0 pbw, based on 100 pbw of component (A). Preferably, component (C) is present in an amount ranging from 2.0 to 3.75 pbw, more preferably 2.1 to 3.5 pbw, even more preferably 2.2 to 3.2 pbw, and most preferably 2.3 to 3.0 pbw, based on 100 pbw of component (A). The effect of limiting or further limiting the amount of component (C) to the above range is to further improve laser light transmittance at a thickness of 2.0 mm, while further suppressing deterioration of mechanical properties.

[0041] Preferably, the laser-weldable fiber-reinforced polyester composition of the present invention contains component (C) in an amount ranging from 1 to 3.3 wt%, based on the total weight of the composition. This is based on the requirement that the amount of component (C) be 1.75 to 4.50 parts by weight, based on 100 parts by weight of component (A), or a narrower range, be met. The amount of component (C) can be, for example, as low as 1.1 wt%, 1.2 wt%, 1.5 wt%, or 1.8 wt%, or as high as about 1.1 wt%, about 1.2 wt%, about 1.5 wt%, or about 1.8 wt%, or as high as 3.0 wt%, 2.7 wt%, or 2.5 wt%, or about 3.0 wt%, about 2.7 wt%, or about 2.5 wt%, based on the total weight of the composition.

[0042] Examples of suitable amounts of components (A), (B) and (C) in the laser-weldable fiber-reinforced polyester composition according to the present invention are as follows: - 100 pbw of (A), 100 pbw of (B) and 2.0 pbw of (C), corresponding to 49.505 wt% of (A), 49.9 wt% of (B) and 0.990 wt% of (C); - 100 pbw of (A), 100 pbw of (B) and 3.75 pbw of (C), corresponding to 49.080 wt% of (A), 49.080 wt% of (B) and 1.840 wt% of (C); - 100 pbw of (A), 15 pbw of (B) and 2.0 pbw of (C), corresponding to 85.470 wt% of (A), 12.821 wt% of (B) and 1.709 wt% of (C); - 100 pbw of (A), 15 pbw of (B) and 3.75 pbw of (C), corresponding to 84.211 wt% of (A), 12.632 wt% of (B) and 3.158 wt% of (C); - 100 pbw of (A), 35 pbw of (B) and 3 pbw of (C), corresponding to 72.464 wt% of (A), 25.362 wt% of (B) and 2.174 wt% of (C); and - 100 pbw of (A), 70 pbw of (B) and 2.3 pbw of (C), corresponding to 58.038 wt% of (A), 40.627 wt% of (B) and 1.335 wt% of (C). The weight percentages (wt%) are based on the total amount of components (A), (B), and (C). If no additional components are present in the composition, the weight percentages are also based on the total weight of the composition.

[0043] Compositions according to the present invention have high transmittance, at least in the near-infrared (NIR) region at wavelengths typically applied in laser welding processes, more particularly in the wavelength range of 800-1200 nm. In certain embodiments, the compositions have a transmittance of at least 25.0%, more particularly at least 30.0%, and even more particularly at least 40%, measured at a thickness of 1.2 mm and 980 nm by the procedure described in the TMG3 User Manual Version 3.0 (herein referred to as the TMG3 Method and described further herein (Experimental Part)). In other specific embodiments, the compositions have a transmittance of at least 15.0%, more particularly at least 17.5%, and even more particularly at least 20.0%, measured at a thickness of 2.0 mm and 980 nm by the TMG3 Method further described herein. Permeability measurements are performed on injection-molded plaques with different thicknesses: 1.2 mm (75 x 50 mm plaques), 2.0 mm, or 3.0 mm (80 x 80 mm plaques). Injection molding is performed using standard PBT molding conditions.

[0044] The transmittance of the composition in the visible region (VR), at wavelengths in the range of about 400 to 700 nm, can vary over a wide range and can be as high as in the NIR, but can also be significantly lower, depending on the further additives present.

[0045] The laser-weldable fiber-reinforced polyester composition of the present invention can optionally contain one or more additional additives in addition to components (A), (B), and (C). These one or more additional additives are collectively referred to herein as component (D). These one or more additional additives may be any auxiliary additive used in the fiber-reinforced polyester composition. Examples include particulate fillers such as glass beads, amorphous silica, asbestos, calcium silicate, calcium metasilicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, barium sulfate, and feldspar; other fibers, i.e., fibers other than glass fibers, such as aramid fibers and potassium titanate fibers; processing aids, stabilizers such as heat stabilizers, light stabilizers, and antioxidants; lubricants and mold release agents; colorants such as dyes and pigments; and plasticizers.

[0046] The additive or additives can be added at any desired stage during the preparation of the composition by any suitable conventional method. The additives may, for example, be added separately, as a premix with one or more other components, or as a masterbatch. Preferably, the additive or additives are added as a masterbatch comprising the additive or additives dispersed in the PBT resin.

[0047] The one or more further additives of component (D) are preferably used in an amount such that they do not enhance, or only enhance to a limited extent, the laser light transmittance and / or mechanical properties of the composition. Preferably, the polyester composition of the present invention contains component (D), if any, in an amount ranging from at most 20 wt%, preferably at most 15 wt%, and most preferably from 0 to 10 wt%, based on the total weight of the composition. If used, the particulate filler is preferably present in an amount ranging from at most 15 wt%, preferably at most 10 wt%, and more preferably from 0 to 5 wt%, based on the total weight of the composition. If used, other fibers are preferably present in an amount ranging from at most 15 wt%, preferably at most 10 wt%, and more preferably from 0 to 5 wt%, based on the total weight of the composition.

[0048] Also more preferably, the combined amount of particulate filler and other fibers is in the range of 0 to 15 wt%, even more preferably 0 to 10 wt%, and most preferably 0 to 5 wt%, based on the total mass of the composition. Furthermore, fibers and fillers with high laser light absorption, such as carbon fibers, carbon black, graphite, graphene, or carbon nanotubes, are preferably present in an amount less than 1 wt%, more preferably in the range of 0 to 0.25 wt%, and particularly preferably in the range of 0 to 0.05 wt%, based on the total mass of the composition.

[0049] Preferably, the composition according to the invention consists of: - component (A) in an amount ranging from 40 to 85 wt%; - component (B) in an amount ranging from 15 to 49.5 wt%; - component (C) in an amount ranging from 1 to 3.3 wt%; - component (D) in an amount ranging from 0 to 20 wt%; Weight percentages (wt%) are based on the total weight of the composition.

[0050] The compositions according to the invention may be neutral, i.e., free of colorants, or may be colored, i.e., contain colorants such as pigments or dyes.

[0051] Suitable colorants include both organic and inorganic pigments and / or dyes. Inorganic pigments such as titanium dioxide, ultramarine blue, iron oxide, and carbon black can also be added. Organic pigments such as phthalocyanines, quinacridones, perylenes, and dyes, such as nigrosine and anthraquinone, as well as other colorants, can be added if they do not absorb within the range of the laser used. Otherwise, these colorants can only be used in small amounts that still allow at least partial transmission of the laser light. Colorants such as soot and carbon black can also be used, but preferably in very small amounts, preferably less than 0.1 wt%, more preferably less than 0.05 wt%, based on the total weight of the composition.

[0052] Examples of inorganic pigments are antimony trioxide, antimony pentoxide, basic lead carbonate, basic lead sulfate or lead silicate, lithopone, titanium dioxide (anatase, rutile), zinc oxide, zinc sulfide, metal oxides such as Berlin blue, lead chromate, lead chromate sulfate, chromium antimony titanate, chromium oxide, iron oxide, cobalt blue, cobalt chrome blue, cobalt nickel grey, manganese blue, manganese violet, molybdate orange, molybdate red, nickel antimony titanate and ultramarine, metal sulfides such as antimony trisulfide, cadmium sulfide, cadmium selenide sulfide, zirconium silicate, zirconium vanadium blue, zirconium praseodymium yellow.

[0053] Examples of organic pigments are anthraquinone, azo, azomethine, benzanthrone, quinacridone, quinophthalone, dioxazine, flavanthrone, indanthrone, isoindoline, isoindolinone, methine, perinone, perylene, phthalocyanine, pyranthrone, pyrrolo-pyrrole, thioindigo pigments and, for example, metal complexes of azo, azomethine, methine dyes, or metal salts of azo compounds, metal complexes of azo, azomethine or methine dyes, azomethine, quinacridone, dioxazine, isoindoline , isoindolinone, perylene, phthalocyanine, pyrrolo-pyrrole and thioindigo colorants and bismuth vanadate, anthraquinone-based, such as alkylamino, amino, arylamino, cyclohexylamino, hydroxy, hydroxyamino or phenylmercapto-anthraquinone, triphenylmethane dyes, and fluorescent dyes, such as those of the benzothiazole, coumarin, oxaline or thiazine type, pyrazolone, perinone and anthraquinone methine, azo and coumarin type.

[0054] In a particular embodiment, the laser-weldable fiber reinforced polyester composition according to the invention comprises a laser-transparent colorant, which is understood herein to be a colorant that absorbs light in the visible range at wavelengths below 800 nm and transmits light in the infrared range from 800 nm to 1200 nm.

[0055] Suitably, the composition comprises the laser light transparent colorant in an amount in the range of 0.1 to 3 wt%, preferably 0.2 to 2.0 wt%, more preferably 0.3 to 1.5 wt%, based on the total weight of the composition.

[0056] The laser transparent colorant in this particular embodiment of the present invention may be any colorant or a combination of different colorants. Preferably, the laser transparent colorant is a black colorant or a non-black colorant, or any combination thereof. Non-black laser transparent colorants may have any color, such as, for example, a red colorant, a yellow colorant, a green colorant, a blue colorant, or a purple colorant.

[0057] In a preferred embodiment of the present invention, the laser-weldable fiber reinforced polyester composition comprises a single black laser transparent colorant, or a combination of a black laser transparent colorant and at least one non-black laser transparent colorant, or a combination of at least two non-black laser transparent colorants that provide a black color. Such a combination of at least two non-black laser transparent colorants that provides a black color is also referred to herein as a "black color combination."

[0058] In the present specification, black is understood as a color having an L* value, measured according to the method in accordance with ISO 7724-1-2-3, of at most 35. Accordingly, in the present specification, a "black coloring combination" of colorants is understood as a combination of colorants that provides a composition comprising said combination of colorants with a color having an L* value, measured according to the method in accordance with ISO 7724-1-2-3, of at most 35.

[0059] More preferably, the composition comprises a black pigmented combination of two or more different non-black laser transparent colorants. The advantages of a composition comprising a black pigmented combination of two or more different non-black laser transparent colorants are that it can produce molded parts with a black impression (equivalent to soot coloring) and very good surface quality, the composition retains high laser transparency in the range of unpigmented materials, and is suitable for many welding applications requiring dark or black parts.

[0060] Such black coloring combinations preferably contain a mixture of colorants of different colors, i.e., colorants that absorb at different wavelengths in the visible range below 800 nm. There are many examples of colorant combinations that can be used to produce black coloring combinations. Examples of dyes that can be used as non-black laser-transmitting colorants in such combinations are described, for example, in EP1240243A1. Generally, blue, purple, and green dyes can be the main components for producing black dyes. For example, combinations of blue dyes, red dyes, and yellow dyes; combinations of green dyes, red dyes, and yellow dyes; combinations of blue dyes, green dyes, red dyes, and yellow dyes; and combinations of green dyes, purple dyes, and yellow dyes can be used. Examples include pyrazolones, perinones, anthraquinones, such as anthraquinone green dyes, anthraquinone blue dyes, or anthraquinone purple dyes; methine, azo, and coumarin dyes; metal-containing pigments, such as inorganic pigments; metal complexes of azo, azomethine, or methine dyes, azomethines, quinacridones, dioxazines, isoindolines, isoindolinones, perylenes, phthalocyanines, pyrrolopyrroles, and thioindigo dyes; quinophthalone dyes; and metal azo dyes. More specifically, neutral anthraquinone dyes imparting blue, purple, or green can be used as the main component of a black coloring combination by mixing them with potentially used red and then yellow dyes. Dyes belonging to the monoazo complex dyes can be mixed with an anthraquinone dye to produce a black dye for use as a colorant in the composition. In other black coloring combinations, the colorant amine salt of an anthraquinone dye can be combined with a second dye selected from the group consisting of perinone dyes, monoazo complex dyes, anthrapyridone dyes, and anthraquinone dyes.

[0061] Suitably, the composition comprises a black coloured combination of at least two laser light transparent colourants in a total amount in the range of 0.1 to 3 wt %, preferably 0.2 to 2.0 wt %, more preferably 0.3 to 1.5 wt %, based on the total weight of the composition.

[0062] In a preferred embodiment, a composition comprising a black colored combination of at least two non-black laser light transparent colorants has a maximum transmittance of 10% in at least a spectral subrange of the VIS spectral range (the wavelength range of light from 400 nm to 700 nm).

[0063] In a further preferred embodiment of the present invention, the laser-transparent fiber-reinforced polyester composition is a black composition having an L* value of at most 35, preferably at most 33, more preferably at most 32. The value of the color parameter L* is measured by a method according to ISO 7724-1-2-3. The lower limit of L is 0 for a completely black material, and preferably L is at least 5.

[0064] In certain preferred embodiments, the composition according to the present invention is a black composition having a transmittance of at least 25.0%, more particularly at least 30.0%, and even more particularly at least 40%, measured at a thickness of 1.2 mm and 980 nm by the method according to TMG3, as further described herein. Even more preferably, the composition further has a transmittance of at least 15.0%, more particularly at least 17.5%, and even more particularly at least 20.0%, measured at a thickness of 2.0 mm and 980 nm by the method according to TMG3, as further described herein.

[0065] The present invention also relates to a method for preparing the inventive laser-weldable fiber-reinforced polyester composition, which composition, as well as the specific and preferred embodiments thereof described hereinabove, can be produced by processes known per se by melt-mixing the starting components (A), (B) and (C), and also the optional component (D), in the amounts as indicated above for the inventive composition or its various embodiments.

[0066] The method according to the present invention comprises the steps of melting a polybutylene terephthalate resin and blending (A) 100 parts by weight of the polybutylene terephthalate resin; (B) 15 to 100 parts by weight of glass fiber; and (C) 1.75 to 4.5 parts by weight of an alkali metal salt of a fatty acid having 24 to 40 carbon atoms. The melt blending can be carried out in conventional blending equipment such as a single-screw extruder, a twin-screw extruder, a Brabender mixer, or a Banbury mixer, and the blend is then extruded. The extrudate can be cooled and optionally pelletized, granulated, crushed, or otherwise reduced to particles or fragments. The blending temperature is preferably 230 to 290°C. The components can be added simultaneously or separately. For example, components (A), (C), and (D) can be added to a first extruder inlet, mixed, and heated, and component (B) can be added to a second extruder inlet and combined with the mixed components (A), (C), and (D).

[0067] The present invention also relates to a method for producing a molded part from a laser-weldable fiber-reinforced polyester composition, which method comprises the step of molding a laser-weldable fiber-reinforced polyester composition into a preformed shape, the laser-weldable fiber-reinforced polyester composition being according to the present invention or any of the specific or preferred embodiments thereof described hereinabove. The laser-weldable fiber-reinforced polyester composition of the present invention can be molded by processes known per se: molded parts can be produced, for example, by injection molding. In such processes, conventional equipment and conventional process conditions can be used.

[0068] The present invention also relates to laser-transparent molded parts made from a laser-weldable fiber-reinforced polyester composition, the laser-weldable fiber-reinforced polyester composition being a composition according to the present invention or any of its various embodiments described herein above.

[0069] The molded parts are suitable for the production of laser-welded products. The laser transmittance of these molded parts, measured at a thickness of 1.2 mm and 980 nm by the method according to TMG3, as described further herein (Experimental Part), is preferably at least 25.0%, more particularly at least 30.0%, and even more particularly at least 40%. The molded parts also preferably have a transmittance of at least 15.0%, more particularly at least 17.5%, and even more particularly at least 20.0%, measured at a thickness of 2.0 mm and 980 nm by the method according to TMG3, as described further herein (Experimental Part).

[0070] The advantages of these molded parts are that they not only exhibit an overall good balance of laser light transmission and mechanical properties, i.e., tensile strength, tensile elongation at break, and / or impact resistance, but also require shorter laser welding cycle times to reach a predetermined level of weld strength, or reach higher weld strengths at a predetermined laser welding cycle time, compared to other molded parts made from other fiber-reinforced PBT compositions with similar laser light transmission but based on other transmission-enhancing additives.

[0071] These advantages are further enhanced in compositions having 1.9 to 4.0 pbw of component (B), better still 2.0 to 3.75 pbw of component (B), more particularly 2.1 to 3.5 pbw of component (B), and even more particularly 2.2 to 3.0 pbw of component (B), based on 100 pbw of component (A).

[0072] The present invention also relates to a method for producing a composite article by laser welding. Such a method includes irradiating a laser beam onto the interface between a laser-transparent molded part and a laser-light-absorbing polymeric substrate, thereby forming a welded bond between the laser-transparent molded part and the laser-light-absorbing polymeric substrate. The process of laser welding, also known as laser transmission welding, and the equipment used therein are known in the art. The basic principles of laser welding are described in technical references, such as Plastverarbeiter 46 (1995) 9, 42-46; Kunststoffe 87 (1997) 3, 348-350; Kunststoffe 87 (1997) 11, 1632-1640; Kunststoffe 88 (1998) 2, 210-212; and Plastverarbeiter 50 (1999) 4, 18-19. Examples of such methods and the devices used therein are described, for example, in European patent EP 1048439 B1.

[0073] In the method according to the invention, a laser-transparent molded part is made from a laser-weldable fiber-reinforced polyester composition according to the invention, or any of the various embodiments thereof described herein above.

[0074] In the method according to the present invention, a molded part made from the laser-transparent fiber-reinforced polyester composition according to the present invention, or any of the specific embodiments thereof described above, is combined with a laser-light-absorbing polymer substrate and subjected to a laser welding process to form a bonded, laser-welded article. The laser-light-absorbing polymer substrate can be any molded part made from any laser-light-absorbing polymer material. By way of example, it can be a thermoplastic, thermoset, or composite material. Preferably, the laser-light-absorbing polymer substrate is made from a thermoplastic composition comprising a thermoplastic polymer and having suitable laser light absorption in the wavelength range used. The thermoplastic polymer in the laser-light-absorbing polymer substrate is preferably a thermoplastic polymer that is miscible with PBT in the laser-weldable fiber-reinforced polyester composition. More preferably, the thermoplastic composition comprises a thermoplastic polyester. The thermoplastic polyester can be, for example, PBT, PET, or PCT, or any mixture or copolymer thereof. Most preferably, the thermoplastic composition in the laser-light-absorbing polymer substrate comprises PBT.

[0075] The thermoplastic resin composition can be made laser-absorbent by adding inorganic pigments, organic pigments, or fillers, or other additives, or any combination thereof. Suitable additives are known in the art. Examples include carbon fiber, carbon black, graphite, graphene, and carbon nanotubes. Carbon black and graphite are highly effective at absorbing laser light. Either carbon black or graphite, or a combination thereof, is preferably used for the laser-absorbent substrate.

[0076] The advantages of the laser welding process according to the invention as described above for molded parts also apply here, such as a good overall balance between laser light transparency and mechanical properties, short laser welding cycle times or high weld strength.

[0077] The present invention also relates to a composite article comprising a laser-transparent molded part joined by laser welding onto a laser-light-absorbing polymer substrate. The laser-transparent molded part laser-welded onto the laser-light-absorbing polymer substrate is made from the laser-weldable fiber-reinforced PBT composition according to the present invention or any of the various embodiments thereof described hereinabove. The advantages of such an article are that, as reported above, the laser-weldable fiber-reinforced PBT composition not only has a better overall balance of laser-light transparency and mechanical properties, but also that a laser-welded article in which two molded parts are welded together has a higher weld strength at the same applied cycle time, or the same weld strength can be achieved with a shorter laser welding cycle time.

[0078] In a preferred embodiment of the present invention, the laser light absorbing polymer substrate in the composite article and the laser light absorbing polymer substrate used in the laser welding process to make the composite article are made from a thermoplastic composition comprising carbon black and / or graphite and polybutylene terephthalate resin (PBT). [Example]

[0079] The present invention is further illustrated by the following examples and comparative examples.

[0080] result raw materials A1: Polybutylene terephthalate having a melting point of 224±2°C (measured according to the method according to ISO 11357 with a heat ramp of °C / min), a relative solution viscosity (RSV) of 2.36±0.04 dl / g (measured according to the method according to ISO 307 in m-cresol at a concentration of 1 g in 100 g m-cresol at a temperature of 25°C), and a melt volume rate (MVR) of 11.5±1.0 cm3 / 10 min (measured according to the method according to ISO 1133 at 250°C and 2.16 kg). B1: Glass Fiber: E-glass, standard grade chopped fiber for thermoplastic polyester injection molding compounds C1: Sodium salt of montanic acid C2: Sodium stearate (sodium salt of stearic acid) # C3: Sodium myristate (for comparison purposes) # C4: Magnesium salt of montanic acid # C5: Aluminum salt of montanic acid # D1: Black color combination of non-black laser transparent colorants Composition T:BASF LUX B4300 G6 # Composition Laser light absorbing polymer Base material: PBT TV4 261 BK00001 (standard carbon black filled PBT 30wt% glass fiber grade) # C2, C3, C4 and C5 and composition T are not according to the invention and are used herein for comparative purposes only.

[0081] processing combination The molding composition was produced in a ZSK25 twin-screw extruder with a flat temperature profile of 250-260°C and pelletized. Components (A), (B) and (D) were premixed and dosed at the throat, and component (B) was dosed via a side feeder.

[0082] molding Prior to molding, the material was dried in a N2-purged vacuum oven at 120°C for 16 hours. In preparing the test samples, injection molding was performed on a Fanuc-2 injection molding machine, model α-S50iA, equipped with a suitable mold cavity, applying a barrel temperature of 260°C and a mold cavity temperature of 90°C. - For the laser light transmittance test, test samples measuring 75 x 50 mm and 1.2 mm in thickness, and test samples measuring 80 x 80 mm and 2.0 mm and 3.0 mm in thickness, respectively, were prepared. - For tensile testing, test samples were prepared according to ISO 527-1A. - For unnotched impact testing, test samples were prepared according to ISO 179 / 1eU. - For the laser welding test, a test sample with the dimensions of the cover of an automotive radar mold housing and a thickness of 1 mm was prepared.

[0083] Laser welding Laser welding was performed using the process and equipment described in European Patent EP1048439B1, with laser power (200W, 250W, and 300W; W = watts), welding speed (1000mm / s, 2000mm / s, and 4000mm / s), and clamping pressure (3.1N / (mm 2 ), 6.2N / (mm 2 ) and 9.2N / (mm 2 )) using low, medium, and high settings.

[0084] Test Method Laser light transmittance measurement Laser light transmission was measured on injection-molded test samples with thicknesses of 1.2 mm (75 × 50 mm plaques), 2.0 mm (80 × 80 mm plaques), and 3.0 mm (80 × 80 mm plaques) using a TMG3 measurement unit equipped with a laser source emitting light with a wavelength of 980 nm, applying the procedure described in the TMG3 User Manual Version 3.0 (herein referred to as the TMG3 method). The TMG3 measurement unit was provided by LPKF WeldingQuipment GmbH, Alfred-Nobel-Strasse 55-57, 90765 Furth, Germany.

[0085] Mechanical properties - Tensile strength and elongation at break were determined in tensile tests carried out at 23°C and at a stretching rate of 5 mm / min according to the method in accordance with ISO 527-1A(2019). - Charpy unnotched impact resistance was determined at 23°C according to the method in accordance with ISO 179 / 1eU.

[0086] viscosity The relative solution viscosity of the polymer was measured in m-cresol at a concentration of 1 g in 100 g of m-cresol at a temperature of 25° C. by a method according to ISO 307.

[0087] Color parameters The color parameter L* was measured on plaques used in the laser light transmittance test at 23°C by a method according to ISO 7724-1-2-3, measured using a Minolta CM-3700d spectrophotometer using a xenon light source.

[0088] Composition and Test Results Compositions according to the invention (Examples) and compositions of comparative properties (Comparative Examples), as well as the test results obtained for these Examples and Comparative Examples, are reported in Tables 1 to 5.

[0089] [Table 1]

[0090] The test data show surprisingly good results in both laser light transmittance and mechanical properties for the example compositions according to the present invention. For composition CE-B, which contains approximately 1 pbw of sodium montanate (component C1), laser light transmittance shows a relatively small increase compared to composition CE-A, which contains only PBT, glass fiber, and additive D but does not contain component C1. However, laser light transmittance increases sharply when the amount of component C1 exceeds 1 pbw, reaching a laser light transmittance 3.5 to 4 times higher than that of CE-A for composition EX-II, which contains 2.61 pbw of component C1. For compositions containing more than 2.61 pbw of component C1, laser light transmittance plateaus and gradually decreases, but even at a component C1 content of 4.26 pbw (EX-V), laser light transmittance remains higher than that of CE-B, while mechanical properties remain at a good level. When the content of component C1 was 4.86 pbw (CE-U), the laser light transmittance was slightly reduced but still higher than that of CE-B, but the impact resistance was reduced to less than 50% of that of comparative examples CE-A and CE-B.

[0091] [Table 2]

[0092] [Table 3]

[0093] [Table 4]

[0094] The mechanical properties of the compositions of the examples according to the present invention, i.e., tensile strength, elongation at break, and unnotched Charpy impact resistance, are better than those of the comparative examples using the corresponding amounts of sodium stearate (component C2) or sodium myristate (component C3). For all three components C1, C2, and C3, the tensile strength, elongation at break, and unnotched Charpy impact resistance tend to decrease as the content of C1, C2, and C3 increases, respectively. However, components C2 and C3 show similar trends, differing from the trend of component C1 in that the decrease begins at a lower amount and / or the decrease in measured values is greater. For component C1, the decrease begins at a higher content and / or the decrease in measured values is smaller.

[0095] Furthermore, simple laboratory tests showed that the laser light transmittance of the comparative examples corresponding to compositions based on the magnesium salt of montanic acid (component C4) and the aluminum salt of montanic acid (component C5) was very low, comparable to or even lower than the composition of comparative example A (CE-A) and certainly much lower than the laser light transmittance of the compositions of Examples I to V.

[0096] Some of the test results are also shown in Figures 1 to 4.

[0097] As can be seen in all three graphs (Figures 2, 3, and 4), sodium stearate (C2) and sodium myristate (C3) show a sharp decline in elongation at break and unnotched impact resistance at 0.5 pbw or 1 pbw content, based on 100 pbw PBT, and a sharp decline in tensile strength at 1.5 pbw content, based on 100 pbw PBT. In all three graphs, sodium myristate (C3) performed slightly better than sodium stearate (C2) in compositions with Cx contents ranging from 0.5 to 2.5 pbw, based on 100 pbw PBT. Meanwhile, properties were much better retained in compositions containing sodium montanate (C1). Even at a content of 4.5 pbw of sodium montanate (C1) based on 100 pbw of PBT, all three properties, tensile strength, elongation at break and unnotched impact resistance, are retained at a higher level than a composition having a content of 1.5 pbw of sodium stearate (C2) based on 100 pbw of PBT.

[0098] [Table 5]

[0099] Table 5 shows the laser light transmittance and welding test results for two examples (EX-III and EX-IV) and two comparative examples (CE-A and CE-T). CE-A is a fiber-reinforced polyester composition that does not contain additives to enhance laser light transmittance, while CE-T is a commercially available product with high transmittance but unknown composition.

[0100] The data in the table show surprisingly good results in terms of welding behavior for Examples II and III, which are representative of compositions according to the invention, where the performance is much better than the two comparative examples, which is not surprising considering that CE-A lacks additives to enhance laser light transmission, but is very surprising for CE-T, which itself has relatively high laser light transmission.

Claims

1. (A) Polybutylene terephthalate resin (PBT), (B) glass fibers, and (C) Alkali metal salts of fatty acids having 24 to 40 carbon atoms 1. A laser-weldable fiber reinforced polyester composition comprising:

1. A laser-weldable fiber-reinforced polyester composition, wherein component (B) is present in an amount ranging from 15 to 100 parts by weight, based on 100 parts by weight of component (A), and component (C) is present in an amount ranging from 1.75 to 4.50 parts by weight, based on 100 parts by weight of component (A).

2. 2. The laser-weldable fiber-reinforced polyester composition of claim 1, wherein the polybutylene terephthalate resin (A) is a PBT homopolymer or a PBT copolymer containing at least about 85 mol of copolymerized units of butylene (butylene units) and terephthalate (terephthalate units) and at most about 15 mol of copolymerized units of an additional comonomer (comonomer units), wherein the molar percentages (mol) of butylene units, terephthalate units, and comonomer units are all based on the total molar amount of the moles of butylene units, moles of terephthalate units, and moles of comonomer units in the copolymer.

3. 3. The laser-weldable fiber-reinforced polyester composition according to claim 1, wherein the polybutylene terephthalate resin (A) has a relative solution viscosity (RSV) in the range of 1.5 to 2.8 dL / g, measured in m-cresol at a concentration of 1 g in 100 g m-cresol at a temperature of 25°C according to a method according to ISO 307.

4. 4. The composition of any one of claims 1 to 3, wherein component (B) is present in an amount ranging from 25 to 80 parts by weight (pbw), preferably from 30 to 70 pbw, and more preferably from 35 to 60 pbw, based on 100 pbw of component (A).

5. 5. The composition of any one of claims 1 to 4, wherein the alkali metal in component (C) is sodium or potassium, or a combination thereof.

6. 6. The composition according to any one of claims 1 to 5, wherein the fatty acid in component (C) is a fatty acid having from 26 to 36 carbon atoms, preferably from 28 to 32 carbon atoms.

7. 7. The composition of any one of claims 1 to 6, wherein component (C) is present in an amount ranging from 2.0 to 3.75 parts by weight (pbw), based on 100 pbw of component (A), more preferably from 2.1 to 3.5 pbw, even more preferably from 2.2 to 3.2 pbw, and most preferably from 2.3 to 3.0 pbw.

8. - 40-85 wt% of component (A); - 15 to 49.5 wt% of component (B); - 1 to 3.3 wt% of component (C); and - 0 to 20 wt. % of one or more additives (component (D)); 8. The composition of claim 1, wherein the weight percentages (wt%) are based on the total weight of the composition.

9. 9. The composition of any one of claims 1 to 8, comprising a laser transparent colorant, preferably a black laser transparent colorant, or a black colored combination of two or more different non-black laser transparent colorants.

10. 10. The composition of any one of claims 1 to 9, having a laser light transmittance measured at 980 nm by the method according to TMG3 described herein above of at least 25.0%, preferably at least 30.0%, more preferably at least 40% at a thickness of 1.2 mm, or at least 15.0%, preferably at least 17.5%, and more preferably at least 20% at a thickness of 2.0 mm.

11. 1. A method for preparing a laser-weldable fiber-reinforced polyester composition by melt blending, the method comprising the steps of melting a polybutylene terephthalate resin and blending (A) 100 parts by weight of the polybutylene terephthalate resin, (B) 15 to 100 parts by weight of glass fiber, and (C) 1.75 to 4.5 parts by weight of an alkali metal salt of a fatty acid having 24 to 40 carbon atoms.

12. 12. The method of claim 11, wherein the laser-weldable fiber-reinforced polyester composition is a composition according to any one of claims 1 to 10.

13. 1. A method of making a molded part from a laser-weldable fiber reinforced polyester composition, comprising forming a laser-weldable fiber reinforced polyester composition into a preformed shape, wherein the laser-weldable fiber reinforced polyester composition comprises: (A) polybutylene terephthalate resin, (B) glass fibers, and (C) Alkali metal salts of fatty acids having 24 to 40 carbon atoms wherein, based on 100 parts by weight of component (A), component (B) is present in an amount ranging from 15 to 100 parts by weight and component (C) is present in an amount ranging from 1.75 to 4.5 parts by weight.

14. 14. The method of claim 13, wherein the laser-weldable fiber-reinforced polyester composition is a composition according to any one of claims 1 to 10.

15. (A) polybutylene terephthalate resin, (B) glass fibers, and (C) Alkali metal salts of fatty acids having 24 to 40 carbon atoms wherein, based on 100 parts by weight of component (A), component (B) is present in an amount ranging from 15 to 100 parts by weight, and component (C) is present in an amount ranging from 1.75 to 4.5 parts by weight.

16. 16. The laser-transparent molded part according to claim 15, wherein the laser-weldable fiber-reinforced polyester composition is a composition according to any one of claims 1 to 10.

17. 11. A method for producing a composite article by laser welding, comprising the step of irradiating a laser beam at an interface between a laser-light-transmissive molded part and a laser-light-absorbing polymeric substrate, thereby forming a weld bond between the laser-light-transmissive molded part and the laser-light-absorbing polymeric substrate, wherein the laser-light-transmissive molded part is made from the laser-weldable fiber-reinforced polyester composition of any one of claims 1 to 10.

18. 11. A composite article comprising a laser-transparent molded part joined by laser welding to a laser-light-absorbing polymer substrate, wherein the laser-transparent molded part is made from the laser-weldable fiber reinforced polyester composition of any one of claims 1 to 10.

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