Laser welded object, process for preparing a laser welded object and composition used therein

Abstract

The present invention relates to a laser-welded object, to a laser- transmission welding process, and to a laser-transparent polymer composition used therein, which comprises at least a combination of (A) a polybutylene terephthalate resin (PBT resin); and (B) a di-alkali-metal alkali metal salt of norbornane-2,3- dicarboxylic acid, or a substituted derivative thereof; and / or a polyester copolymer comprising repeat units, derived from the di-alkali-metal salt, or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer).

Description

[0001] LASER WELDED OBJECT, PROCESS FOR PREPARING A LASER WELDED OBJECT AND COMPOSITION USED THEREIN

[0002] This invention relates to a laser-welded object, as well as to a process for preparing a laser-welded object, and to a polymer composition for use in a molded part for laser welding. More particular, the invention relates to a laser-welded object, obtainable by laser-transmission welding, as well as to a process for preparing a laser-welded object by means of laser-transmission welding, and to a laser- transparent polymer composition. The invention further relates to a process for preparing the laser-transparent polymer composition, to a process for preparing a laser-transparent molded part, to use of the laser-transparent molded part in a lasertransmission welding process, and to use of the laser-welded object. The laser- transparent polymer composition in the laser-welded object according to the invention comprises at least a polyester resin, more particularly a polybutylene terephthalate resin.

[0003] There are various processes for welding molded plastic parts, such as hotplate welding, vibration welding and laser welding, more particular the process known as laser-transmission welding. Laser-transmission welding is a method providing an alternative to other welding technologies such as vibration welding and hotplate welding and has seen a constant increase in its use in recent times, in particular with utilization of diode lasers, for plastics mainly lasers in the Near IR wavelength region are used. Laser-weldable polyester compositions are known from the prior art and are described in various patents or patent applications.

[0004] Laser-transmission welding is described in further detail in, for example US2011 / 0288220A1. The process requires a molded plastic part which exhibits transparency for the wavelength of the laser light, as well as a molded plastic part which exhibits laser absorbance. Laser-welded parts as such, as well as laser- transparent polymer compositions for use in laser-transmission welding processes are known. Laser-transparent parts and laser-transparent polymer compositions comprising a polyester resin used therein are for example described in US2011 / 0288220A1 and US2008 / 0153957A1.

[0005] According to US2011 / 0288220A1, polyesters, and in particular polybutylene terephthalate (PBT), are materials with several good properties for various applications, but exhibit particularly low laser-transparency and a high level of beam expansion, due to its semi-crystalline morphology. For that reason, PBT and other polyesters have been comparatively little used as material for laser-welded components, although other aspects of its property profile (e.g., good dimensional stability and low water absorption) make it very attractive for applications of this type. Also according to US2011 / 0288220A1 , materials that crystallize rapidly, such as PBT, also provide processing advantages, in particular quick demoldability and therefore short cycle times. It is therefore desirable to combine semi-crystallinity with rapid crystallization and high laser-transparency. Although various attempts have been undertaken to improve the laser-transparency of polyesters, the effects achieved with those attempts as reported in US2011 / 0288220A1 were overall relatively minor and therefore not entirely satisfactory, or showing other serious disadvantages such as that an increase in laser-transparency is achieved with loss of mechanical properties.

[0006] The thermoplastic molding compositions proposed by US2011 / 0288220A1 and reported to be suitable for producing laser-transparent moldings, comprise, next to a polyester resin, 0.05 to 2.0 wt.% of Na2CO3, K2CO3, NaHCO3, KHCO3, or a mixture of these, as essential components. The lasertransparency of these compositions is significant and preferably is at least 33% (at 1064 nm, measured on moldings of thickness 2 mm).

[0007] A disadvantage of these compositions, however, is that the increased laser-transparency still comes at a cost of mechanical properties. In other words, also these compositions show a loss of mechanical properties, compared to corresponding compositions not comprising the said essential components. This is seen in a reduced impact resistance accompanied with a significantly lower strain-at-break for unreinforced formulations and in a reduced impact resistance accompanied with a slightly lower strain-at-break for reinforced formulations.

[0008] Other laser-weldable polyester compositions are described in, for example, US2008 / 0153957A1. The compositions of US2008 / 153957A1 comprise (A) a polybutylene terephthalate (PBT) resin and (B) a fatty acid compound in an amount in the range of 0.01 to 1.0 part by weight (pbw), preferably about 0.03 to 0.5 pbw, relative to 100 pbw of PBT resin. The fatty acid compound suitably is a fatty acid ester, a fatty acid amide or a metal salt of C12-36 fatty acid. The metal salt of the C12-36 fatty acid may include, for example, singly or in combination, an alkali metal salt (e.g., a sodium salt and a potassium salt), an alkaline earth metal salt (e.g., a magnesium salt and a calcium salt), a salt of a metal of the group 2B of the Periodic Table of Elements (e.g., a zinc salt), and a salt of a metal of the group 3B of the Periodic Table of Elements (e.g., an aluminum salt). According to US2008 / 0153957A1 , the addition of the fatty acid-series compound to the resin composition in a specific low proportion as described above efficiently ensures improvement of the laser-transmissivity, while with a lower proportion of the fatty acid-series compound, improvement of the laser-transmissivity is not enough, while, on the other hand, with a higher proportion of the fatty acid-series compound, there is a possibility that the laser-transmissivity is deteriorated. The composition of US2008 / 0153957A1 may comprise further components, such as fibers and fillers and other auxiliary additives for PBT-based polyester compositions.

[0009] However, in the examples in US2008 / 0153957A1, component (B) showed a moderate effect on the transparency.

[0010] For laser-transmission welding, it is important that the laser- transparent polymer composition exhibits sufficient laser-transparency, as well as sufficient mechanical properties. If the laser-transparency is insufficient, defects such as an insufficient weld strength and / or burn marks may be obtained, which should be avoided. It is generally known that the physical properties (such as glass transition and melting temperature, viscosity, etc.) and mechanical properties (such as toughness) of polymers depend on the molecular weight of the polymer. The lower the molecular weight is, the lower the transition temperatures, the viscosity, and the mechanical properties will be. Retention of molecular weight during compounding and further processing is therefore very important. The retention of sufficient mechanical properties can be related to maintaining the viscosity of the polymer, such as measured, for example, by the method for measuring the relative solution viscosity (RSV).

[0011] It is therefore an object of the present invention to provide a laser- welded object comprising a laser-transparent part, and a laser-welding process for preparing the laser-welded object, wherein the laser-transparent part comprises a laser transparent polymer composition that exhibits sufficient laser-transparency in combination with sufficient mechanical properties for the molded parts and improved retention of RSV of the polyester. It is a further object of the present invention to provide a laser transparent polymer composition and a molded part made thereof, that exhibits sufficient laser-transparency in combination with sufficient mechanical properties and improved retention of RSV.

[0012] Surprisingly, these objects have been achieved with different embodiments according to the invention, involving a laser-welded object, as well as a laser transparent polymer composition, and a laser transparent molded part made thereof, and processes for making the same. The laser-welded object according to the invention comprises two molded parts, (P1) and (P2), welded together by means of laser-transmission welding, wherein

[0013] The first molded part (P1) comprises a laser-transparent polymer composition (I); and

[0014] The second molded part (P2) comprises a laser-absorbent polymer composition (ii); wherein the laser-transparent polymer composition (I) comprises:

[0015] (A) A polybutylene terephthalate resin (PBT resin); and

[0016] (B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or

[0017] - A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer).

[0018] The invention also relates a laser transparent polymer composition comprising

[0019] (A) A polybutylene terephthalate resin (PBT resin); and

[0020] (B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof (component (B)); and / or

[0021] - A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer); and at least one component being selected from (C) and (D), with (C) being glass fibers; and (D) being a colorant.

[0022] It has surprisingly been found by the inventors, based on various experiments, that polyester compositions comprising a di-alkali-metal metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof, in combination with the PBT resin, show a significant improvement in laser-transparency and a very good retention in RSV. The laser-transparency is generally more than sufficient for use in laser welding processes. Furthermore, molded parts made of the polyester compositions comprising the PBT resin (component (A)) and the di-alkali- metal salt of norbornane-2,3-dicarboxylic acid, and / or substituted derivative thereof (B), show good mechanical properties, as illustrated with a high elongation-at-break for fiber-reinforced polyester compositions comprising glass fibers next to component (A) and component (B). This is exemplified in the examples further below.

[0023] Corresponding compositions according to US2011 / 028822A1, comprising disodium carbonate (Na2CO3), instead of a component (B), also show a significant improvement in laser-transparency, some even more so than with a component (B), but the retention in RSV is by far less good. In particular at higher amounts of additive, there is a significant reduction in RSV. Furthermore, the elongation-at-break for fiber- re info reed polyester compositions with Na2CO3 is lower than for corresponding compositions comprising component (B). The inventors have also tested alkali metal salts of other aliphatic mono- and dicarboxylic acids, including sodium montanate, disodium oxalate and disodium succinate. Sodium montanate is an alkali-metal salt of the C12-36 fatty acid according to US2008 / 0153957A1. In contrast to the effects of component (B), these other additives either failed in raising the lasertransmission, some even reducing the laser-transmission, or were much worse in terms of reduction in RSV and / or in elongation-at-break, even compared to Na2CO3. For sodium montanate a much higher amount than reported in US2008 / 0153957A1 was needed to raise the laser-transmission, but this was accompanied with a significant reduction in RSV and elongation-at-break.

[0024] Compositions comprising PBT and the disodium salt of norbornane- 2,3-dicarboxylic acid (also referred to as disodium;bicyclo[2.2.1]heptane-2,3- dicarboxylate, or disodium bicyclo[2.2.1]heptane-2,3-dicarboxylate; commercially available as Hyperform HPN68L from Milliken; CAS number 23838-83-7) are known and for example described in US2019 / 0375933A1 and US6465551 B1. US2019 / 0375933A1 describes disodium bicyclo[2.2.1]heptane-2,3-dicarboxylate, amongst many other components including talc and sodium montanate, as nucleating agent in polyester compositions. This document is directed to the production of very small parts, such as having a material volume of less < 1 ml, and is concerned in particular about the dimensional stability thereof. The compositions of US2019 / 0375933A1 typically contain at least 0.01 and at most 2.00 wt.% of the nucleating agent, and a very high content in polyester polymer, of which preferably > 95 wt.%, more preferably > 98 wt.%, consists of PBT. US2019 / 0375933A1 is silent about laser-transparency of the compositions with sodium montanate and HPN68L, as well as on any effect of these nucleating agents on the RSV of the polyester. US2019 / 0375933A1 is also silent about any filled or reinforced or colored composition, let alone any suggestion about the suitability of any such compositions for use in a transmission-laser welding process.

[0025] US6465551B1 describes the use of bicyclo[2.2.1]heptane dicarboxylate salts as polyolefin nucleators. Herein it is s mentioned that the use of the nucleating agents is not restricted to polyolefins, and may also give beneficial nucleation properties to polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), as well as polyamides such as Nylon 6, Nylon 6,6, and others. Although a general description is given of experiments of blending the nucleating agent in a PET bottle grade resin, no specific examples or any properties are given.

[0026] EP2949703A1 describes the use of polyester compositions for use in laser-transmission welding applications. The compositions of EP2949703A1 comprise 30 - 100 wt.% of a first polyester (70 - 99.9 wt.%) and a polyethylene terephthalate (PET) (0.01 - 30 wt.%), 0 - 5 wt.% of a phosphorus-containing compound and 0 - 70 wt.% of further additives. The first polyester is different from the PET, and is in particular PBT. To increase the laser-transparency of polyester, in particular PBT, the polyester is blended with the PET. For the PET, it is also possible to use PET copolymers which are e.g. modified with various other monomers or derivatives thereof. EP2949703A1 mentions a long list, including norbornane-2,3-dicarboxylic acid, but does not mention further details on these other monomers, nor any comments on any effect thereof on the laser-transparency. Furthermore, EP2949703A1 is silent about the use of alkali salts of norbornane-2,3-dicarboxylic acid, or derivatives thereof in the polyester compositions, or the effect thereof on the laser-transparency of PBT based compositions.

[0027] Ranges, laser-transparency, and other expressions

[0028] It is noted that in expressions wherein a range with an upper limit and / or a lower limit is mentioned, the range explicitly includes any value within the range as well as the mentioned upper limit and the mentioned lower limit. For example, in ‘an amount in the range of 0.2 - 5.0 wt.%, the range explicitly includes 0.2 wt.% and 5.0 wt.% and any value between 0.2 wt.% and 5.0 wt.%.

[0029] The words ‘and / or’ as used in an expression like ‘feature (a) and / or feature (b)’ have the same meaning as expressed by, and can be replaced the words ‘feature (a) or feature (b), or a combination of feature (a) and feature (b)’; thus meaning that any of either feature (a), or feature (b), or both feature (a) and / or feature (b), can be applicable. Thus, in the laser-transparent polymer composition in the various embodiments according to the present invention, comprising the PBT resin (A) and the di-alkali-metal salt (B), and / or the A / B copolymer, the composition may comprise the A / B copolymer, which may be present either next to components (A) and (B); or instead of components (A) and (B); thus replacing part of or all of components (A) and (B).

[0030] The words “at least one component being selected from” means that only one of the listed components after “at least one component being selected from” may be present, as well as a combination of the components listed or even all components listed after “at least one component being selected from”.

[0031] The words ‘one or more’ as used in an expression like ‘one or more further components’ have the same meaning as expressed by, and can be replaced the words ‘one or more than one’, and ‘more than one’ can be, for example, two, three, four, five, seven, ten, etc.

[0032] With the terms ‘laser-transparent’ and ‘laser-transparency’ used herein is understood the ‘laser-light-transparent’ respectively ‘laser-light-transparency’. With a laser-transparent polymer composition is herein understood a composition that exhibits a laser-transparency of at least 25.0 %, measured on a test specimen of 1 mm thickness for laser-light-wavelength of 980 nm by the method according to TMG3 as described herein further below (experimental part). The injection molding is done using standard PBT molding conditions (experimental part).

[0033] The laser-transparent polymer composition

[0034] The laser-transparent polymer composition used in the laser-welded object according to the invention, and used in the process for making the same, comprises at least

[0035] (A) A polybutylene terephthalate resin (PBT resin); and

[0036] (B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or the A / B copolymer thereof.

[0037] The composition may further comprise other components such as glass fibers, colorants, and / or further components. In a specifically preferred embodiment of the composition according to the invention, and molded parts made thereof that can be used in the laser-welded object and in the process for making the same, the composition comprises, next to components (A) and (B), at least glass fibers (component (C)), or a colorant (component (D)), or a combination thereof.

[0038] A / B Copolymer

[0039] Without wishing to be bound by any theory, the inventors believe that carboxylic acid salts or carbonate salts may react with the polymeric chain of the PBT resin (component (A)). And further to that, in order to explain the difference between component (B) and the other carboxylic and carbonate components, that such reactions may generally lead to chain scission reactions, resulting in a lower average molecular weight and lower RSV. Furthermore, as what the inventors believe could be an explanation for the difference, component (B) might be able to react further and build in, into the polymeric chain of the PBT resin, thereby restoring some or most of the molecular weight and surprisingly making the composition exhibiting both sufficient laser-transparency as well as better retention of RSV and sufficient mechanical properties, as is exemplified in the examples below.

[0040] As a result of such reactions, the composition may also comprise a polyester copolymer comprising repeat units derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof, incorporated in the PBT resin. Such repeat unit may be referred to as norbornane-2,3-dicarboxylato repeat units, whereas such copolymer derived from the PBT resin and comprising norbornane-2,3-dicarboxylato repeat units is herein referred to as A / B copolymer. The expression “norbornane-2,3-dicarboxylato repeat units” includes the substituted derivatives thereof when these are also referred to under component (B).

[0041] Accordingly, the inventors expect component (B) to be present in the composition, either as such, or incorporated in the A / B copolymer, or as a combination thereof. This is reflected in the expression ’’component (B) is present, either as such and / or incorporated in the A / B copolymer” as used further herein.

[0042] Therefore, with the amount of component (B) being present in the composition, expressed either in wt.% or in parts by weight, is herein understood the amount including any part of component (B) incorporated in the A / B copolymer. And where the amount is expressed relative to the combined amount of components (A) and (B), this includes, if any, the A / B copolymer.

[0043] Even though component (B) could be present in the form of repeat units incorporated in the PBT resin, and thus be part of the A / B copolymer, the molar amount, and thereby the wt.% of component (B) in the composition, if to be established afterwards, can be measured by proton nuclear magnetic resonance (1H-NMR).1H- NMR is also suited for determination of the ratio of the amount of component (B) present as such and the amount of component (B) present in the form of repeat units incorporated in the PBT resin. The established afterwards, can be measured by proton nuclear magnetic resonance (1H-NMR).1H-NMR is described in the experimental part.

[0044] Correspondingly, with the amount of component (A) being present in the composition, expressed either in wt.% or in parts by weight, is herein understood the combined amount of components in the PBT resin and including any part of component (A) in the A / B copolymer, while excluding any parts or repeat units derived from component (B) incorporated in the A / B copolymer. The amounts of component (A) and component (B) reported herein below, thus correspond with the respective amounts used for the preparation of the composition, which can be made by meltmixing, and thus are irrespective of any further reaction between the two.

[0045] Component (A) Polyester

[0046] Component (A) in the laser-transparent polymer composition according to the present invention is a polybutylene terephthalate (PBT) resin. The polybutylene terephthalate resin suitably is a PBT homopolymer or a PBT copolymer, or a combination thereof. The PBT homopolymer consists mainly of copolymerized units of butylene and terephthalate. Such a homopolymer can suitably be prepared by copolymerization of butane diol and terephthalic acid, wherein these monomers are used as the only monomers. The PBT homopolymer may contain other copolymerized units resulting from traces of other components; for example, trace impurities in the butane diol and / or terephthalic acid, or trace impurities formed during the polycondensation of butane diol and terephthalic acid. Suitably the PBT homopolymer consists of at least 99 mole % of butylene units and terephthalate units, and at most 1 mole% of other copolymerized units, relative to the total molar amount of butylene units, terephthalate units and other copolymerized units.

[0047] Component (A) may comprise or consist of a PBTcopolymer. This PBT copolymer is different from the A / B copolymer mentioned herein above, in that it does not contain repeat units derived from norbornane-2,3-dicarboxylic acid, or a substituted derivative, or an alkali metal salt thereof. The PBT copolymer of component (A) may comprise other comonomers and such comonomers may be copolymerized into the copolymer chain in minor amounts. Examples of such other comonomers include difunctional monomers, i.e. , monomers with two reactive sites, such as other diacids, for example isophthalic acid, other diols, such as ethylene glycol, and functional comonomers, for example 5-sodium sulphoisophthalate. Difunctional comonomers are suitably present, if at all, in an amount of up to about 10 mol %, or up to about 5 mol%. Comonomers that have more than two reactive sites, for example trimellitic anhydride, trimellitic acid, pyromellitic dianhydride (pmda), and pentaerythritol, may suitably be incorporated as branching agents to increase the melt viscosity. Such comonomers having more than two reactive sites are suitably present, if at all, in an amount of up to about 5 mol%, or even better up to about 2.0 mol%. Suitably, the PBT copolymer contains 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 further comonomers (comonomer units). Examples of further comonomers that may be copolymerized into the PBT copolymer are, for example, isophthalic acid, propylene glycol and butylene glycol. Preferably, the PBT copolymer contains at least about 90 mol %, more preferably at least about 95 mol %, or even more preferably at least about 98 mol %, of butylene units and terephthalate units; and correspondingly preferably at most about 10 mol %, more preferably at most about 5 mol %, or even more preferably at most about 2.0 mol %, of comonomer units. Herein the mol percentages (mol%) of butylene units, terephthalate units and comonomer units are all relative to the total molar amount of moles of butylene units, moles of terephthalate units and moles of comonomers units in the copolymer.

[0048] In a preferred embodiment, the PBT resin (component (A)) in the laser-transparent polymer composition is a PBT homopolymer, or a PBT copolymer containing at least 98 mol % of copolymerized units of butylene and terephthalate, and at most about 2.0 mol % of copolymerized units of comonomers, relative to the total molar amount of moles of butylene units, moles of terephthalate units and moles of comonomers units in the copolymer.

[0049] The polybutylene terephthalate resin (component (A)) used for the preparation of the composition according to the invention may be any polybutylene terephthalate resin commonly used for preparing thermoplastic polyester molding compositions. The resin may have properties, such as viscosity and melt flow ratio, varying accordingly. Suitably, the polybutylene terephthalate resin has a relative solution viscosity as high as about 2.8, or even higher than 2.8, or as low as about 1.5, or even lower than 1.5. Preferably, the PBT resin has a RSV in the range of 1.8 - 2.6, more preferably in the range of 1.9 - 2.3. Herein, the relative solution viscosity (RSV) is measured in m-cresol at a concentration of 1 g in 100 g m-cresol at a temperature of 25 °C by the method according to ISO 307.

[0050] The advantage of the PBT resin having a lower viscosity is that the laser-transparent polymer composition has improved processing behavior, while the advantage for a higher viscosity is that molded parts made of the composition has better mechanical properties. The advantage of the PBT resin having a viscosity in the preferred range is that the composition combines good processing behavior and good mechanical properties. The advantage of the PBT resin having a viscosity in the more preferred range is that the composition has an even better balance in processing behavior and mechanical properties.

[0051] Suitably, the laser-transparent polymer composition comprises component (A) in an amount of at least 35 wt.%, in which the weight percentage (wt.%) is with respect to the total weight of the composition. The amount of component (A) can be as high as 99.8 wt.%, relative to the total weight of the composition. The amount can be, for example, as low as, or about, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, or 58 wt.%, or as high as, or about, 99.5 wt.%, 99 wt.%, 98 wt.%, 95 wt.%, 90 wt.% 80 wt.%, 75 wt.%, or 70 wt.%, relative to the total weight of the composition.

[0052] Suitably, the amount of component (A) is in a range of 35 - 99.8wt.%, or in subranges thereof. For example, the amount of component (A) is in a range of 35 - 90 wt.%, more particular 40 - 85 wt.%, relative to the total weight of the composition. This range is in particular preferred for embodiments wherein the composition further comprises at least glass fibers (component (C).

[0053] Alternatively, the amount of component (A) is in a range of 85 - 99.8 wt.%, more particular 90 - 99.5 wt.%, relative to the total weight of the laser- transparent polymer composition. This range is in particular preferred for the embodiments wherein the composition further comprises at least a colorant (component (D).

[0054] Component (B) Di-alkali-metal salt

[0055] The laser-transparent polymer composition in the various embodiments according to the present invention comprises a di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof (component (B)). Norbornane-2,3-dicarboxylic acid is a compound having a bicyclic structure comprising seven carbon atoms bearing two carboxylic acid groups, one each at the 2 and 3 position, and ten hydrogen atoms, one each at the 1,2,3 and 6 position, and two each at the 4,5 and 7 position. In the substituted derivative of the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, one or more of the hydrogen atoms may be substituted by a substituent. The substitution can be single or multiple, at any of the 1-7 positions: 1 , 2, 3 and 6 single 4, 5 and 7 single or double; and any combination thereof. Substituents can be selected from the group consisting of alkyl groups, aryl groups (e.g. phenyl), alkylphenyl groups, hydroxy groups, amine, halogen, alkoxy groups, alkenoyl groups, alkylamines, and carbocylic groups. Preferably, the substituted derivative preferably comprises one or more alkyl groups as substituent, more preferably one or more methyl groups, and even more preferably one or two methyl groups. Most preferably, the di-alkali-metal salt is a di-alkali-metal salt of norbornane- 2,3-dicarboxylic acid; i.e. the unsubstituted version with all positions except for the two carboxylic groups occupied by hydrogen.

[0056] In the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, the alkali metal can be any alkali metal, and suitably is selected from the group consisting of lithium, sodium and potassium, or any combination thereof. Preferably, the alkali metal comprises sodium or potassium, or a combination thereof, more preferably comprises sodium, or even consists of sodium. Preferably, the di-alkali-metal salt comprises the disodium salt, and most preferably, the alkali metal salt consists of disodium norbornane-2,3-dicarboxylate.

[0057] Component (B) is suitably present in an amount in a range of 0.2 - 6.0 parts by weight (pbw), preferably 0.3 - 5.0 pbw, more preferably 0.4 - 4.0 pbw, relative to 100 pbw of the combined amount of components (A) and (B). The amount of component (B) is also suitably in a range of 0.2 - 5.0 wt.%, preferably 0.25 - 4.0 wt.%, more preferably 0.3 - 3.0 wt.%, relative to total weight of the composition. Herein component (B) may be present, as mentioned above, either as such and / or incorporated in the A / B copolymer, and the combined amount of components (A) and (B), includes, if any, the A / B copolymer. A higher amount of component (B) is advantageously applied for a higher laser-transparency, whereas a lower amount has the advantage of even better retention of the RSV of the polyester. The more preferred range offers an optimal combination in high laser-transparency and good retention of the RSV of the polyester.

[0058] Component (C) Glass fibers

[0059] The composition in various embodiments according to the present invention may be non-reinforced, i.e., not comprising a reinforcing agent, or may be reinforced, i.e., comprising a reinforcing agent, such as glass fibers or glass flakes. In a preferred embodiment of the composition according to the present invention, the composition comprises glass fibers (component (C)).

[0060] For the glass fibers (component (C), any glass fibers suitable for use in fiber- re info reed polyester compositions and in 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 a fiber-reinforced laser-transparent polymer composition according to the present invention may have a length varying over a wide range. These can be used in the form of rovings or of chopped glass in the forms commercially obtainable. The glass fibers can be added as continuous fibers or as cut or ground glass fibers, it being possible for the fibers to be equipped with a suitable sizing system and an adhesion promoter or adhesion promoter system, for example based on silane. Particular preference is given here to glass fibers in the form of E-glass (alumino-borosilicate glass with less than 1 wt.% alkali oxides mainly used for glass-reinforced plastics), but also other types of glass fibers may be used, such as A-glass (alkali-lime glass with little or no boron oxide), E-CR-glass (alumino-lime silicate with less than 1 wt.% alkali oxides, has high acid resistance), C-glass (alkali- lime glass with high boron oxide content used, for example for glass staple fibers), D- glass (borosilicate glass with high dielectric constant), R-glass (alumino silicate glass without MgO and CaO, with high mechanical requirements), and S-glass (alumino silicate glass without CaO but with high MgO content with high tensile strength).

[0061] With a fiber is herein understood a material consisting of particles having a three-dimensional elongated body having a length (L), a diameter (D) and a thickness (T), and having an aspect ratio (L / D) defined as its length (L) divided by its diameter (D) of at least 10. Herein the elongated body has a cross-section, perpendicular to the length of the elongated body, defined by the diameter (D) and thickness (T). The cross-section can be circular or non-circular. In case of a noncircular cross-section the diameter (D) is the largest dimension of the cross-section, and the thickness (T) is the smallest dimension of the cross-section. In case of a circular cross-section the diameter (D) and the thickness (T) are equal.

[0062] Suitably, the glass fibers have a median aspect ratio (L / D) of at least 15: 1 , preferably at least 20: 1. The glass fibers suitably have a fiber diameter between 3 and 20 pm (micrometer). The glass fibers may have cross sections with different shapes. The glass fibers suitably have a circular cross section. These glass fibers may have a number average diameter of, for example, about 7 pm, about 8 pm, or about 9 m, or about 10 pm, or about 12 pm, or about 15 pm. Preferably, the number average diameter is in the range of 8 - 15 pm, more preferably in the range of 9 - 12 pm. The glass fibers may also have a non-circular cross section, for example an oblong cross section or an ellipsoid oblong cross section. A non-circular cross section is herein characterized by a cross-section with different diameters in different directions.

[0063] Suitably, the glass fibers having a non-circular cross section have a cross section with a largest diameter of for example, about 5 pm, or about 8 pm, or about 9 pm, or about 10 pm, or about 12 pm, or about 15 pm, or about 18 pm. Preferably, the number average value of the largest diameter is in the range of 9 - 18 pm, more preferably in the range of 10 - 15 pm.

[0064] The glass fibers (component (C)) in the preferred embodiments of the laser-transparent polymer composition may be present in an amount varying over a wide range. The amount can be, for example, as low as, or about, 15 wt.% 10 wt.%, or 5 wt.% or even lower; or as high as, or about, 30 wt.%, 35 wt.%, 40 wt.% 45 wt.%, 50 wt.%, or even higher, relative to the total weight of the composition. Preferably, the laser-transparent polymer composition according to these embodiments comprises component (C) in an amount in the range of 5 - 50 wt.%, more preferably 10 - 45 wt.%, even more preferred 15 - 40 wt.%, relative to the total weight of the composition.

[0065] Component (C), i.e. , the glass fibers, if used at all, is suitable present in an amount in the range of 10 - 100 pbw, relative to 100 pbw of the combined amounts of components (A) and (B). Preferably the amount of component (C) is in the range of 20 - 80 pbw, more preferably 30 - 70 pbw, even more preferably 35 - 60 pbw, relative to 100 pbw of the combined amounts of components (A) and (B). A higher minimum amount of component (C) has the advantage that the mechanical properties of the composition are better, more particularly that the tensile strength is higher. A lower maximum amount of component (C) has the advantage that the laser light transparency of the composition is better.

[0066] Component (D) Colorant

[0067] The composition in various embodiments according to the present invention may be neutral in color, i.e., not comprising a colorant, or may be colored, i.e., comprising a colorant, such as a pigment or dye. In a preferred embodiment of the composition according to the present invention, the composition comprises a colorant (component (D)). Both organic and inorganic pigments and / or dyes are suitable as colorants. Inorganic pigments such as titanium dioxide, ultramarine blue, iron oxide and carbon black; furthermore organic pigments such as phthalocyanines, quinacridones, perylenes and dyes such as nigrosine and anthraquinones may be used as colorants, as well as other colorants can be added if these do not absorb in the range of the laser used. Alternatively, they may only be used in such small quantities that at least partial transmission of the laser light is still possible. Colorants such as soot and carbon black may be used but preferably only in very small amounts: preferably below 0.1 wt.%, more preferably below 0.05 wt.%, or even below 0.02 wt.%, or 0.01 wt.%, relative to the total weight of the composition.

[0068] Examples of inorganic pigments are antimony trioxide, antimony pentoxide, basic lead carbonate, basic lead sulphate or lead silicate, lithopone, titanium dioxide (anatase, Rutile), zinc oxide, zinc sulphide, metal oxides such as berlin blue, lead chromate, lead sulphochromates, chromium-antimony-titanate, chromium oxides, iron oxides, cobalt blue, cobalt-chromium blue, cobalt-nickel grey, manganese blue, manganese violet, molybdate orange, molybdate red, nickel-antimony-titanate and ultramarine, metal sulphides such as antimony trisulfide, cadmium sulphide, cadmium sulphoselenide, zirconium silicates, zirconium vanadium blue, zirconium praseodymium yellow.

[0069] Examples of organic pigments are antrachinone, azo, azomethine, benzanthron, quinacridone, quinophthalone, dioxazine, flavanthrone, indanthrone, isoindoline, isoindolinone, methine, perinone, perylene , phthalocyanine, pyranthrone, pyrrolo-pyrrole, thioindigo pigments and metal complexes of e.g. 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 series, for example alkylamino, amino, arylamino, cyclohexylamino, hydroxy, hydroxyamino or phenylmercapto- anthraquinones, triphenylmethane dyes, and fluorescent dyes, for example those from the benzothiazole, coumarin, oxarin or thiazine series, pyrazolone, perinone and anthraquinone methine, azo and coumarin type.

[0070] In a particular embodiment, the laser-transparent polymer composition according to the invention comprises a laser-light-transparent colorant. With a laser-light-transparent colorant is herein understood a colorant that absorbs light in the visible light region at a wavelength of less than 800 nm and transmits light in the infra-red region at 800 nm to 1200 nm.

[0071] Suitably, the composition comprises the laser-light-transparent colorant in an amount in the range of 0.01 - 5 wt.%, 0.1 - 3 wt.%, preferably 0.2 - 2.0wt.%, more preferably 0.3 - 1.5 wt.%, relative to the total weight of the composition.

[0072] The laser-light-transparent colorant in this embodiment of the invention may be of any color, or combination of colorants of different colors. Suitably the laser-light-transparent colorant is a black colorant or a non-black colorant, or any combination thereof. The non-black laser-light-transparent colorant may have any color, for example: a red colorant, a yellow colorant, a green colorant, a blue colorant, or a violet colorant.

[0073] In a preferred embodiment of the invention, the laser-transparent polymer composition comprises a single black laser-light-transparent colorant, or a combination of a black laser-light-transparent colorant and at least one non-black laser- light-transparent colorant, or a combination of at least two non-black laser-light- transparent colorants providing a black color. Such a combination of at least two non- black laser-light-transparent colorants providing a black color is herein also referred to as ‘black-coloring combination’.

[0074] With a black color is herein understood a color with an L*-value, measured by the method according to ISO 7724-1-2-3, of at most 35. Accordingly, with a ‘black-coloring combination’ of colorants is herein understood a combination of colorants that provides a composition comprising said combination of colorants, a color with an L*-value, measured by the method according to ISO 7724-1-2-3, of at most 35.

[0075] More preferably, the composition comprises a black-coloring combination of two or more different non-black laser-light-transparent colorants. The advantage of the composition comprising a black-coloring combination of two or more different non-black lapser-light-transparent colorants is that molded parts with a black color impression (comparable to coloring with soot) and very good surface quality can be produced, the composition retains a high laser light transparency in the range of non-colored material and is suitable for many welding applications requiring dark colored or black parts.

[0076] Such a black-coloring combination suitably comprises a mixture of colorants with different colors, i.e. , absorbing at different wavelength in the visible region below 800 nm. There are many examples of combinations of mixed colorants that can be used to result in a black-coloring combination. Examples of dyes that can be used as non-black laser-light-transmitting colorants in such combinations are described, for example in EP1240243A1. Generally, dyes which exhibit blue, violet, and green colors can be main components to produce the black dyes. For instance, the combination of blue dye, red dye, and yellow dye; the combination of green dye, red dye and yellow dye; the combination of blue dye, green dye and red dye and yellow dye; and the combination of green dye, violet dye and yellow dye can be used. Examples thereof are combinations selected from the dyes from pyrazolone; perinone; anthraquinone, for example an anthraquinone green dye, an anthraquinone blue dye or an anthraquinone violet dye; methine, azo, and coumarin type; metal-containing pigments, such as inorganic pigments; metal complexes of azo, azomethine or methine dyes, azomethine, quinacridone, dioxazine, isoindoline, isoindolinone, perylene, phthalocyanine, pyrrolopyrrole and thioindigo type; quinophthalone dyes; metallic azo. More particular, neutral anthraquinone dyes imparting blue, violet, or green can be used as a major component of the resulting black-coloring combination by being mixed with red and then yellow dyes, may be used. Dyes belonging to monoazo complex dyes can be mixed with the anthraquinone dyes to produce a black dye for use as colorants in the composition. In other black-coloring combinations, a colorant amine salt of 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.

[0077] Suitably, the composition comprises the black-coloring combination of at least two laser-light-transparent colorants in a total amount in the range of 0.1 - 3 wt.%, preferably 0.2 - 2.0wt.%, more preferably 0.3 - 1.5 wt.%, relative to the total weight of the composition.

[0078] In a preferred embodiment, the composition comprising the blackcoloring combination of the at least two non-black laser-light transmitting colorants has a transmission of at most 10% at least in spectral sub-ranges in the VIS spectral range (wavelength range of light from 400 nm to 700 nm).

[0079] In a further preferred embodiment of the invention, the laser- transparent polymer composition is a black composition having an L*-value of at most 35, preferably at most 33, more preferably at most 32. Herein the values for the color parameter L* is measured by the method according to ISO 7724-1-2-3. A lower limit of L is 0 for a perfect black material, preferably L is at least 5.

[0080] In a particular preferred embodiment, the composition according to the invention is a black composition having a transparency of at least 25.0 %, preferably at least 30.0 %, more particular at least 35.0 %, and even more particular at least 40%, measured at 1.0 mm thickness and 980 nm by the method according to TMG3 as described herein further below. Even more preferably, the composition has further a transparency of at least 15.0 %, more particular at least 17.5%, even more particular at least 20.0 %, measured at 2.0 mm thickness and 980 nm by the method according to TMG3 as described herein further below. Herein the transparency measurement is done on injection molded plaques with a thickness of 1.0 mm, respectively 2.0 mm.

[0081] The transmission of the composition in the visible region (VR) at wavelengths in the range of about 400 - 700 nm, can vary over wide range and may be as high as in the NIR, but may also be much lower, depending on further additives present.

[0082] Component (E) Further components

[0083] The laser-transparent polymer composition used in the present invention comprising components (A) and (B), and specific embodiments thereof comprising components (C) and / or (D), may optionally comprise one or more further components, or further additives. These one or more further components are herein jointly referred to as component (E). These one or more further components may be any auxiliary additive, or combination of auxiliary additives, used in polyester compositions. Examples thereof are particulate fillers, for example: glass beads, amorphous silica, asbestos, calcium silicate, calcium metasilicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, barium sulphate, and feldspar; other fibers, i.e. , fibers different from glass fibers, for example: aramid fibers and potassium titanate fibers; processing aids; stabilizers, for example: heat stabilizers, light stabilizers and antioxidants; lubricants and mold-release agents; and plasticizers, etc.

[0084] The additive or additives can be added at any desired stage by any suitable conventional manner during the preparation of the composition. Herein the additives may be added, for example, separately, or as a premix with one or more other components, or as a masterbatch. Suitably, the additive or additives are added as a masterbatch, comprising the additive or additives dispersed in a PBT resin.

[0085] The one or more further additives of component (E) are preferably used in such an amount that these do not corroborate, or only in limited extend, the laser light transparency and / or the mechanical properties of the composition. Suitably, component (E) is present in the laser-transparent polymer composition, if at all, in an amount of at most 20 wt.%, preferably at most 15 wt.%, and most preferred in the range of 0 - 10 wt.%, relative to the total weight of the composition. The particulate fillers, if used at all, are suitably present in an amount of at most 15 wt.%, preferably at most 10 wt.%, and more preferably 0 - 5 wt.%, relative to the total weight of the composition. The other fibers, i.e. , fibers different from glass fibers, if used at all, are also suitably present in an amount of at most 15 wt.%, preferably at most 10 wt.%, and more preferably 0 - 5 wt.%, relative to the total weight of the composition. Suitably, the other fibers have a median aspect ratio of at least 15:1 , preferably at least 20:1 , and / or a fiber diameter between 3 and 20 pm (micrometer).

[0086] A filler is herein understood to be a particulate material consisting of particles having a three dimensional shape defined by a length (L), a diameter (D) and a thickness (T) and having an aspect ratio of L / D (length / diameter) of less than 10:1. Herein the length (L) is the largest of the three dimensions, and a thickness (T) is the smallest of the three dimensions, and diameter (D) can be either in-between the length (L) and the thickness (T), or equal to the length (L), or equal to the thickness (T), or, in case of spherical particles, equal to both the length (L) and the thickness (T). Suitably, the granular material has a median aspect ratio of about 5:1 or less.

[0087] Preferably, the combined amount of particulate fillers and other fibers, is in the range 0 - 15 wt.%, even more preferably 0 - 10 wt.% and most preferred 0 - 5 wt.%, relative to the total weight of the composition. Furthermore, fibers and fillers that have high laser light absorbency, for example carbon fibers, graphite, graphene, or carbon nanotubes, are preferably present in an amount below 1 wt.%, more preferably in an amount in the range of 0 - 0.25 wt.%, and particularly preferably in an amount in the range of 0 - 0.05 wt.%, relative to the total weight of the composition.

[0088] Examples of compositions according to the invention

[0089] In a particular embodiment of the present invention, the laser- transparent polymer composition consists of

[0090] 40 - 94.8 wt.% component (A);

[0091] 0.2 - 5 wt.% of component (B);

[0092] 5 - 50 wt.% component (C);

[0093] 0 - 5 wt.% of component (D); and 0 - 20 wt.% component (E); wherein the weight percentages (wt.%) relative to the total weight of the composition. In another embodiment of the present invention, the laser-transparent polymer composition consists of

[0094] 40 - 99.79 wt.% component (A);

[0095] 0.2 - 5 wt.% of component (B);

[0096] 0 - 50 wt.% component (C);

[0097] 0.01 - 5 wt.% of component (D); and

[0098] 0 - 20 wt.% component (E); wherein the weight percentages (wt.%) relative to the total weight of the composition.

[0099] One example of a composition according to the invention is one consisting of 99 pbw of component (A), and 1.0 pbw of component (B), and 98 pbw of component (C) Herein component (C) is present in an amount of 49.5 wt.%, relative to the total weight of the composition.

[0100] Another example of a composition according to the invention is one consisting of 98 pbw of component (A), 2.0 pbw of component (B) and 15 pbw of component (C). Herein component (C) is present in an amount of 13.0 wt.%, relative to the total weight of the composition. In case of a composition comprising, next to 98 pbw of component (A), 2.0 pbw of component (B) and 15 pbw of component (C), one or more further components (components (E)), the weight percentage of component (C) can be lower than 13.0 wt.%, relative to the total weight of the composition, for example 10 wt.%.

[0101] Another example of a composition according to the invention is one consisting of 99 pbw of component (A), and 1.0 pbw of component (B), and 2.5 pbw of component (D). Herein component (D) is present in an amount of 2.43 wt.%, relative to the total weight of the composition. Another example of a composition according to the invention is one consisting of 98 pbw of component (A), 2.0 pbw of component (B) and 1.1 pbw of component (D). Herein component (D) is present in an amount of 1.06 wt.%, relative to the total weight of the composition. In case of a composition comprising, next to 98 pbw of component (A), 2.0 pbw of component (B) and 1.1 pbw of component (D), one or more further components (components (E)), the weight percentage of component (D) can be lower than 1.06 wt.%, relative to the total weight of the composition, for example 0.96 wt.%.

[0102] A further example of a composition according to the invention is one consisting of 99 pbw of component (A), and 1.0 pbw of component (B), 98 pbw of component (C) and 2.5 pbw of component (D). Herein component (C) is present in an amount of 48.9 wt.%, relative to the total weight of the composition, while component (D) is present in an amount of 1.25 wt.%, relative to the total weight of the composition. Another example of a composition according to the invention is one consisting of 98 pbw of component (A), 2.0 pbw of component (B), 15 pbw of component (C) and 1.1 pbw of component (D). Herein component (C) is present in an amount of 12.9 wt.%, relative to the total weight of the composition, while component (D) is present in an amount of 0.95 wt.%, relative to the total weight of the composition. In case of a composition comprising, next to 98 pbw of component (A), 2.0 pbw of component (B),15 pbw of component (C), and 1.1 pbw of component (D), one or more further components (components (E)), the weight percentage of component (C) component (D) can be lower than respectively 12.9 wt.% and 0.95 wt.%, relative to the total weight of the composition, for example respectively 11.5 wt.% and 0.85 wt.%.

[0103] The laser-transparent composition in the various embodiment according to the present invention has a laser-transparency of at least 25.0 %, measured at 1 mm thickness and 980 nm by the method according to TMG3 as described herein further below (experimental part). Preferably, the laser-transparency, measured at 1 mm thickness and 980 nm, is at least 30.0 %, more particular at least 35.0 %, and even more particular at least 40.0 %.

[0104] Process for preparing a laser-transparent polymer composition

[0105] The present invention also relates to a process for preparing laser- transparent polymer compositions that can be used in the various embodiments according to the invention. The composition, and any particular or preferred embodiments thereof, as described herein above, can be produced by processes known per se: by melting component (A) and mixing the components (A) and (B), and optionally also component (C) and / or component (D), or further components in the amounts as indicated above for the inventive composition or the various embodiments thereof.

[0106] Herein, the process for preparing a laser-transparent polymer composition, or compounding process, comprises a step of melt-mixing of components comprising

[0107] (A) A PBT resin; and

[0108] (B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and at least one component being selected from (C) and (D), with

[0109] (C) being glass fibers and (D) being a colorant. Suitably, the compounding process comprises melt-mixing of the components in the following amounts

[0110] (A) at least 35 wt.% of component (A); and

[0111] (B) 0.2 - 5.0 wt.% of component (B); and at least one component being selected from (C) and (D), with (C) being glass fibers in an amount of 5 - 50 wt%; and (D) being a colorant in an amount of 0.01 - 2.5 wt% and (E) 0 - 20 wt.% of one or more further components;

[0112] - wherein the weight percentages (wt.%) are relative to the total weight of the composition, and

[0113] - wherein the amount of component (B) is in the range of 0.2 - 6.0 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B).

[0114] Furthermore, herein the combined amounts of components (A) - (E) equals 100 wt.%.

[0115] In a preferred embodiment, the colorant used in the compounding process, comprises, or even consists of a laser-light-transparent colorant; more particular a laser- light-transparent colorant as described herein above.

[0116] The compounding process according to the invention is a melt-mixing process comprising melting of (A) a PBT resin and mixing with (B) a di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof; and optionally either one or more of (C) glass fibers; (D) a colorant; and / or (E) one or more further components. Here the components are suitably selected from the components and in the amounts, and preferred embodiments thereof, mentioned hereabove.

[0117] The melt-mixing can be done in conventional mixing apparatuses, such as single-screw extruders and double screw extruders, Brabender mixers, or Banbury mixers, and then extruding the melted mix of components, thereby resulting in an extrudate. The extrudate can be cooled, and optionally pelletized, granulated, grinded or reduced to particles or fragments otherwise. The mixing temperatures are suitably from 230 to 320°C.

[0118] The components can be added simultaneously, or separately. Suitably, component (A) can be melted first and then be mixed with the other components, or the melting of component (A) and mixing with of one or more of the other components can be done simultaneously, or component (A) can be mixed first with of one or more of the other components, and then be melted. For example, components (A) and (B), and where applicable components (D) and / or (E) can be added to a first extruder inlet and mixed and heated, and component (C) can be added to a second extruder inlet and combined with the mixed components (A) and (B), and optionally (C) and / or (D). Also component (A) can be added to a first extruder inlet and heated, while at component (B), and / or optionally (C) and / or (D) can be added to a second extruder inlet and combined with component (A). Component (B) can also be added in a premixed form; for example, in the form of a masterbatch. Such a masterbatch suitably comprises component (B) and a part of the PBT resin of component (A), while the remainder of the PBT resin of component (A) is added and processed in the melt-mix process as described above.

[0119] Process for preparing a laser-transparent molded part

[0120] The present invention also relates to a process making a molded part from a laser-transparent polymer composition. The process comprises molding a laser- transparent polymer composition into a preformed shape, the laser-transparent polymer composition being according to the present invention or any of the particular or preferred embodiments thereof as described herein above.

[0121] Herein the laser-transparent polymer composition comprises at least

[0122] (A) a PBT resin; and

[0123] (B) a di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or

[0124] - a polyester copolymer comprising repeat units, derived from the di-alkali- metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer).

[0125] Suitably, the laser-transparent composition consists of:

[0126] (A / B) at least 35.2 wt.% of components (A) and (B), and / or if any, the A / B copolymer;

[0127] (C) 0 - 50 wt.% of glass fibers;

[0128] (D) 0 - 2.5 wt.% of a colorant; and

[0129] (E) 0 - 20 wt.% of one or more further components;

[0130] - wherein the weight percentages (wt.%) are relative to the total weight of the composition, and - wherein the amount of component (B) is in the range of 0.2 - 6.0 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B), and if any, the A / B copolymer.

[0131] The composition preferably comprises at least one component being selected from (C) and (D), with (C) being glass fibers in an amount of 5 - 50 wt%; and (D) being a colorant in an amount of 0.01 - 2.5 wt% wherein the weight percentages (wt.%) are relative to the total weight of the composition.

[0132] The laser-transparent polymer compositions of the invention can be molded by processes known per se: the molded parts can be made, for example, by injection molding, molding, compression molding, or pultrusion. The molded part is preferably made by injection molding. For such a process, conventional equipment and conventional process conditions can be used.

[0133] In a preferred embodiment of the molded part, and of the molding process for making a molded part, the colorant comprised by the laser-transparent polymer composition used therein, comprises, or even consists of a laser-light- transparent colorant; more particular a laser-light-transparent colorant as described herein above.

[0134] Laser-transparent molded part

[0135] The present invention also relates to a laser-transparent molded part made of a laser-transparent polymer composition. Herein the laser-transparent polymer composition is a composition according to the present invention, or any of the various embodiments thereof, as described herein above.

[0136] The advantage of these molded parts is not only that these are suitable for use in laser-welding process by means of laser-transmission welding, but also that these parts exhibit an overall better balance in laser light transparency and tensile elongation-at-break of the molded part and retention of relative solution viscosity (RVS) of the PBT resin therein. These advantages are further enhanced for the compositions with component (B) present in an amount in a range of 0.2 - 6.0 parts by weight (pbw), preferably 0.3 - 5.0 pbw, more preferably 0.4 - 4.0 pbw, relative to 100 pbw of the combined amount of components (A) and (B).

[0137] The laser-transparency of these molded parts is preferably at least 25.0 %, more particular at least 30.0 %, and even more particular at least 40%, measured at 1.0 mm thickness and 980 nm by the method according to TMG3 as described herein further below (experimental part). The molded parts preferably also have a transparency of at least 15.0 %, more particular at least 17.5%, even more particular at least 20.0 %, measured at 2.0 mm thickness and 980 nm by the method according to TMG3 as described herein further below.

[0138] Use of a composition, or a molded part made thereof

[0139] The laser-transparent polymer composition according to the present invention and the various particular and preferred embodiments thereof, and molded parts made from these laser-transparent polymer compositions are suitable for producing laser welded products.

[0140] Process for preparing a laser-welded object

[0141] The present invention also relates to a process for producing a laser- welded object by laser-transmission welding, and to a laser-welded object obtainable by laser-transmission welding. Such a process involves the provision of a first molded part (P1 ) comprising a laser-transparent polymer composition (I) and a second molded part (P2) comprising a laser-absorbent polymer composition (II) and arrangement of P1 and P2 to create a contact surface between P1 and P2. The process further comprises irradiating a laser beam on the contact surface, thereby resulting in laser-welded object with P1 and P2 bonded by a laser weld.

[0142] The process of laser welding, also known as laser-transmission welding, and equipment used therein are known in the art. The fundamental principles of laser welding are described in the technical literature, for example in 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. An example of such a process, and apparatus used therein is described, for example, in European patent EP1048439B1.

[0143] In the process according to the invention, comprising at least the steps of: a. Providing a first molded part (P1 ) comprising a laser-transparent polymer composition (I); b. Providing a second molded part (P2) comprising a laser-absorbent polymer composition (II); c. Combining the first part (P1 ) and the second part (P2); and d. Subjecting the combined parts to laser-transmission welding to bond the first molded part (P1 ) to the second molded part (P2); the first molded part (P1) comprises a laser-transparent polymer composition (I) comprising

[0144] (A) A PBT resin; and

[0145] (B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or

[0146] - A polyester copolymer comprising repeat units, derived from the alkali metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (A) (the polyester copolymer referred to as A / B copolymer).

[0147] In the laser-transmission welding process according to the invention, the laser-transparent polymer composition (I) can be any composition comprising the PBT resin (component (A)); the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof (component (B)); and / or the A / B copolymer; and optionally any further component or components, provided the composition has sufficient laser-transparency. The PBT resin (component (A)) can be any PBT resin suitable for use in molding compositions, and preferably is a PBT resin as mentioned herein above. Component (B) suitably is a di-alkali-metal salt of norbornane-2,3- dicarboxylic acid, and / or a substituted derivative thereof, or a preferred embodiment thereof, as mentioned herein above. The further component or components are suitably selected from the components (C), (D) and (E) mentioned herein above. Suitably, the laser-transparent polymer composition (I) is a composition according to the present invention, or any specific embodiment thereof as described above.

[0148] In the laser-transmission welding process according to the invention the first molded part (P1) is combined with a second molded part (P2) comprising a laser-absorbent polymer composition (II). Herein (P1) has the function of a laser- transparent polymeric part and (P2) that of a laser-light-absorbent polymeric substrate. The laser-light-absorbent polymeric substrate can be any molded part made of any laser-light-absorbent polymeric material. By way of example, these can be thermoplastic materials, thermoset materials, or composite materials. Preferably, the laser-light- absorbing polymeric substrate is made of a thermoplastic composition comprising a thermoplastic polymer and having adequate laser light absorption in the wavelength range used. The thermoplastic polymer in the laser-light- absorbing polymeric substrate preferably is a thermoplastic polymer that is miscible with the polyester in the laser-transparent polymer composition (I). More preferably, the thermoplastic composition comprises a thermoplastic polyester. The thermoplastic polyester can be, for example, PBT, or PET, or PCT, or any mixture or any copolymer thereof. Most preferred, the thermoplastic composition in the laser-light-absorbent polymeric substrate comprises PBT.

[0149] The thermoplastic composition can suitably be made laser-light- absorbent by virtue of addition of inorganic pigments, organic pigments, or fillers, or of other additives, or any combination thereof. Suitable additives are known in the art. Examples thereof are carbon fibers, carbon black, graphite, graphene, and carbon nanotubes. Highly effective in absorption of laser light are carbon black and graphite. Either carbon black or graphite, or a combination thereof is preferably used in the laser- light-absorbent substrate.

[0150] For the laser welding process according to the invention, the advantages mentioned above for the molded parts on the overall better balance in laser light transparency and mechanical properties, and the shorter laser welding cycle times or the higher weld strength apply here as well.

[0151] Laser-welded object

[0152] The present invention also relates to a laser-welded object comprising wo molded parts, (P1) and (P2), welded together by means of lasertransmission welding.

[0153] In the laser-welded object according to the invention, the first molded part (P1) comprises a laser-transparent polymer composition (I) and the second molded part (P2) comprises a laser-absorbent polymer composition (II); wherein laser- transparent polymer composition (I) is a composition as mentioned above, and preferably a laser-transparent polymer composition according to the present invention, or any of the various embodiments thereof, as described herein above. The advantage of such laser-welded object is .that the laser-transparent polymer composition has an overall better balance in laser-light-transparency and mechanical properties, as reported above.

[0154] In a preferred embodiment of the invention, the laser-absorbent polymer composition (II) in the laser-welded object and comprised by the molded part (P2) used in the laser welding process for making the laser-welded object is made of a thermoplastic composition comprising and a polybutylene terephthalate (PBT) resin and carbon black and / or graphite. The laser-welded object according to the present invention, and obtainable by the process according to the present invention, is suitable for use in electrical applications, electronics, telecommunications, information-technology, computer, household, sports, medical, motor-vehicle, or entertainment sector.

[0155] The invention further includes electrical components, electronic equipment, household articles, sports attributes, medical devices, motor-vehicles, or entertainment sector, comprising a laser-welded object according to the present invention.

[0156] The invention is further illustrated with the following examples and comparative experiments.

[0157] Experimental part

[0158] Materials

[0159] (A-1) Polyester: Polybutylene terephthalate with a melting temperature of 224±2°C (measured at a heating ramp of 20°C / minute by the method according to ISO11357), a relative solution viscosity (RSV) of 2.36±0.04 dl / g (measured in m-cresol at a concentration of 1 g in 100 g m-cresol at a temperature of 25 °C by the method according to ISO 307) and a melt volume rate (MVR) of 11.5 ± 1.0 cm3 / 10min (measured at 250 °C, 2.16kg by the method according to ISO 1133).

[0160] (B-1) Disodium salt of norbornane-2,3-dicarboxylic acid.

[0161] (B-a) Sodium montanate (sodium salt of montanic acid).

[0162] (B-b) Disodium carbonate.

[0163] (B-c) Disodium oxalate.

[0164] (B-d) Disodium succinate.

[0165] (C-1) Glass Fibers: E-glass, standard grade chopped fibers for thermoplastic polyester injection molding compounds.

[0166] (D-1) Black-coloring combination of non-black laser-light-transparent colorants: eBind LTW-8904 (commercially available from OCI).

[0167] The molding compositions were produced in a ZSK25 twin-screw extruder with a flat temperature profile from 290 to 320°C and with pelletization. Components (A-1) and (B-x) were premixed and dosed at the throat, component (C-1) was dosed at a side feeder.

[0168] Molding

[0169] Prior to molding the materials were dried for 16hrs at 120°C inside a vacuum oven with a N2 purge. For the preparation of the test samples, injection molding was done on a Fanuc-2 injection machine, type a-S50iA, provided with an appropriate mold cavity, and applying a barrel temperature of 260 °C and a mold cavity temperature of 90 °C.

[0170] For the laser light transparency test, test samples of 80x80 mm and a thickness of 1 .0 mm were prepared.

[0171] For the tensile test, test samples according to ISO 527-1A were prepared.

[0172] Test Methods

[0173] Laser Light Transparency Measurement

[0174] The laser-light-transparency was measured on injection molded test samples with a thickness of 1 mm (80x80mm plagues), at the midpoint of the of the plagues, using a TMG3 measuring unit eguipped with laser light source irradiating light with a wavelength 980 nm by applying the procedure as described in the TMG3 User Manual Version 3.0, series number series number 1500209 (herein referred to as method according to TMG3). The TMG3 measuring unit was made available by LPKF WeldingQuipment GmbH, Alfred-Nobel-StraBe 55-57, 90765 Furth Germany.

[0175] The injection molding is done using standard PBT molding conditions, as mentioned above.

[0176] Mechanical Properties

[0177] The tensile elongation-at-break was measured in a tensile test carried out on test-specimen with a thickness of 4 mm at 23°C with a drawing rate of 5 mm / min by the method according to ISO 527-1A (2019).

[0178] Viscosity

[0179] The relative solution viscosity of the polymers was measured in m-cresol at a concentration of 1 g in 100 g m-cresol at a temperature of 25 °C by the method according to ISO 307.1H-NMR

[0180] The1H-NMR method for determining the amount of component (B) in a composition according to or used in the present invention, is exemplified for norbornane dicarboxylic acid disodium salt applied in a PBT homopolymer.

[0181] Approximately 15 mg of the sample was weighed into a 5 mm NMR tube and 0.7 mL of a mixture of CDCh / TFA-d 90 / 10 was added. TFA is trifluoro acetic acid. The tube was then heated to 40 °C under constant rotating for 6 hours until the polymer fraction appeared to be fully dissolved. Then,1H NMR spectra were recorded at 40 °C on a Bruker Avancell I HD 500 MHz spectrometer equipped with a 5 mm broadband cryoprobe. In total, 32 scans were recorded, using 90-degree pulses and a relaxation delay of 60 seconds. For processing, 0.3 Hz line broadening was applied. Baseline correction was done manually using a fifth order polynomial function across the region with the peaks of interest, between 9.5 and -0.5 ppm. Peaks at 8.2 ppm originate from terephthalic acid (TPA) in the PBT resin and correspond to 4 hydrogens per repeat unit. Peaks at about 3.5 and 2.9 ppm originate from norbornane dicarboxylic acid as carboxylate and correspond to 2H each. Peaks at 3.2 and 2.7 ppm originate from norbornane dicarboxylic acid ester and correspond to 2H each as well.

[0182] In the composition, norbornane dicarboxylic acid (NDCA) can be present as carboxylate (NDCA-carboxylate), or esterified, i.e. as an ester (NDCA ester), or both. The norbornane dicarboxylic acid content and degree of esterification were calculated as follows. Integration of the peaks was performed manually. Let lAbe the integral of the terephthalic acid signal; IB the sum of the integrals of the NDCA- carboxylate signals at 3.5 and 2.9 ppm and lc the sum of the integral of the two peaks from NDCA as ester. The degree of esterification (Ester%) is calculated as: Ester% = lc / (IB + lc) * 100%

[0183] Then, the weight percentage of NDCA (NDCA%) is calculated as NDCA% = (IB + lc) * MNDCA I {IA * Mo, PBT+(IB+lc) * MNDCA} * 100% Herein, MNDCA is the molar mass of norbornane dicarboxylic acid disodium salt, 230 g / mol and Mo, PBT is the molar mass of a repeat unit in PBT-homopolymer, 220 g / mol.

[0184] The1H-NMR method, exemplified above for norbornane dicarboxylic acid disodium salt in a PBT homopolymer, can be applied in the same manner for other alkali salts of norbornane dicarboxylic acid as well as for substituted derivatives thereof, adopting the appropriate molecular weight and the appropriate number of hydrogen atoms accordingly. The1H-NMR method can be applied in the same manner for PBT copolymers, correcting the weight percentage of NDCA (NDCA%) by applying the appropriate molar mass of the terephthalic repeat unit and weight percentage thereof in the PBT copolymer. Compositions and test results

[0185] The compositions according to the present invention (Examples) and of comparative nature (Comparative Experiments) and test results obtained with these Examples and Comparative Experiments are reported in Tables 1-3. Table 1 : Compositions and results at 0.5 wt.% additive B-X (Ref: 0 wt.%; Na Montanate (B-a) at 0.75 wt.%)

[0186] Table 2: Compositions and results at 1.0 wt.% additive B-X (Ref: 0 wt.%)

[0187] Table 3: Compositions and results at 2.0 wt.% additive B-X (Ref: 0 wt.%; Na Mon at 1.75 wt.%)

[0188] The results in Tables 1-3 illustrate that the compositions according to the invention (Example I, table I; example II; table 2, Example III, table 3), comprising the disodium salt of norbornane-2,3-dicarboxylic acid in an amount of respectively 0.5 wt.%, 1.0 wt.% and 2.0 wt.%, in combination with the PBT resin, and further all three comprising glass fibers, and Example I and Example III further comprising the blackcoloring combination of non-black laser-light-transparent colorants (D-1), show, compared to the corresponding comparative compositions not comprising the disodium salt (Comparative Experiment CE-A in tables 1 and 3, and CE-B in table 2), a significant improvement in laser-transparency and a very good retention in elongation- at-break and in relative solution viscosity (RSV).

[0189] Compared to other comparative experiments, which comprise instead of the disodium salt of norbornane-2,3-dicarboxylic acid, sodium salts of other carboxylic acids, including disodium salts of other dicarboxylic acids, the compositions of Examples l-lll show the highest elongation-at-break percentages and the highest RSV values. This in combination with the already mentioned high laser-transparency.

[0190] The compositions for the comparative experiments with disodium oxalate (component (B-c)) and disodium succinate (component B-d)) show a somewhat lower retention in RSV, but don’t show an improvement in laser-transparency. This becomes even worse.

[0191] The compositions for the comparative experiments with sodium montanate (component (B-a)) and disodium carbonate (component B-b)) show higher values for the laser-transparency, but lower percentage for the elongation-at-break and a lower retention in RSV. This becomes worse for the higher concentration of 1 wt.% and even more for 2.0 wt.%. For Example III, the composition according to the invention with 2 wt.% of the disodium salt of norbornane-2,3-dicarboxylic acid, the retention in RSV is still relative good, and the elongation-at-break is even the highest of all.

Claims

CLAIMS1. A laser-transparent polymer composition, comprising(A) A polybutylene terephthalate resin (PBT resin; component (A)); and(B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof (component (B)); and / or- A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (the polyester copolymer being referred to as A / B copolymer); and at least one component being selected from (C) and (D), with (C) being glass fibers and (D) being a colorant.

2. A laser-transparent polymer composition according to claim 1 , wherein the PBT resin (component(A)) is: a PBT homopolymer; or a PBT copolymer containing at least 90 mol % of copolymerized units of butylene and terephthalate, and at most 10.0 mol % of copolymerized units of comonomers, relative to the total molar amount of moles of butylene units, moles of terephthalate units and moles of comonomers units in the copolymer.

3. A laser-transparent polymer composition according to claim 1 or 2, wherein components (A) and (B), and, if any, the A / B copolymer, are present in a combined amount of at least 35.2 wt.%, relative to the total weight of the laser- transparent polymer composition.

4. A laser-transparent polymer composition according to any of claims 1-3, wherein component (B) is present, either as such, and / or incorporated in the A / B copolymer, in an amount in the range of 0.2 - 6.0 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B), and, if any, the A / B copolymer.

5. A laser-transparent polymer composition according to any of claims 1-4, wherein the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof (component (B)) comprises disodium norbornane-2,3-dicarboxylate.

6. A laser-transparent polymer composition according to any of claims 1-5, wherein the composition comprises(C) 5 - 50 wt.% of glass fibers; and / or(D) 0.01 - 2.5 wt.% of the colorant; and optionally(E) 0 - 20 wt.% of one or more further components; wherein the weight percentages (wt.%) are relative to the total weight of the composition.

7. A laser-transparent polymer composition according to anyone of claims 1-6, wherein the laser-transparent polymer composition has a laser transparency of at least 25 %, measured at a thickness of 1 mm and by the method according to TMG3 as described herein above.

8. Laser-welded object, comprising two molded parts, (P1) and (P2), welded together by means of laser-transmission welding, whereinThe first molded part (P1) comprises a laser-transparent polymer composition (I); andThe second molded part (P2) comprises a laser-absorbent polymer composition (II); wherein the laser-transparent polymer composition (I) comprises:(A) A polybutylene terephthalate resin (PBT resin); and(B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or- A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer).

9. Laser-welded object according to claim 8, wherein the laser-transparent polymer composition (I) consists of:(A / B) at least 35.2 wt.% of components (A) and (B), and / or, if any, the A / B copolymer thereof; and(C) 0 - 50 wt.% of glass fibers; and / or(D) 0 - 2.5 wt.% of a colorant; and / or(E) 0 - 20 wt.% of one or more further components;- wherein the weight percentages (wt.%) are relative to the total weight of the laser-transparent polymer composition; and- wherein component (B) is present, either as such, and / or incorporated in the A / B copolymer, in an amount in the range of 0.2 - 6.0 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B), and, if any, the A / B copolymer thereof.

10. Laser-welded object according to claim 8 or 9, wherein the laser-transparent polymer composition (I) is a laser-transparent polymer composition according to any one of claims 1-7.

11. Process for preparing a laser-welded object, comprising at least steps of: a. Providing a first part (P1) comprising a laser-transparent polymer composition (I); b. Providing a second part (P2) comprising a laser-absorbent polymer composition (II); c. Combining the first part (P1) and the second part (P2); and d. Subjecting the combined parts to laser-transmission welding to bond the first part (P1) to the second part (P2); wherein the first part (P1) comprises a laser-transparent polymer composition(I) comprising(A) A polybutylene terephthalate resin (PBT resin); and(B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or- A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (the polyester copolymer referred to as A / B copolymer).

12. Use of a laser-welded object according to any of claims 8-10, or obtainable by the process according to claim 11, in an application selected from electrical applications, electronics, telecommunications, information-technology, computer, household, sports, medical, motor-vehicle, or entertainment sector.

13. Process for preparing a laser-transparent polymer composition, the process comprising a step of melt-mixing components comprising(A) A polybutylene terephthalate resin (PBT resin); and(B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and at least one component being selected from (C) and (D), with(C) being glass fibers and (D) being a colorant.

14. Process according to claim 13, comprising melt-mixing of(A) at least 35 wt.% of component (A); and(B) 0.2 - 5.0 wt.% of component (B); and at least one component being selected from (C) and (D), with(C) being glass fibers in an amount of 5 - 50 wt%; and (D) being a colorant in an amount of 0.01 - 2.5 wt%; and optionally(E) 0 - 20 wt.% of one or more further components;- wherein the weight percentages (wt.%) are relative to the total weight of the composition, and- wherein the amount of component (B) is in the range of 0. 2 - 6.0 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B).

15. A process for preparing a laser-transparent molded part, the process comprises steps of: i. Providing a laser-transparent polymer composition comprising(A) A polybutylene terephthalate resin (PBT resin); and(B) A di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or a substituted derivative thereof; and / or- A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt of norbornane-2,3-dicarboxylic acid, and / or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer); ii. Molding the laser-transparent polymer composition by injection molding, or by compression molding, or by pultrusion, to form the molded part; preferably by injection molding.

16. A process according to claim 15, wherein the laser-transparent polymer composition consists of:(A / B) at least 35.2 wt.% of components (A) and (B), and / or, if any, the A / B copolymer;(C) 0 - 50 wt.% of glass fibers;(D) 0 - 2.5 wt.% of a laser transparent colorant; and(E) 0 - 20 wt.% of one or more further components;- wherein the weight percentages (wt.%) are relative to the total weight of the composition, and- wherein the amount of component (B) is in the range of 0.2 - 6.0 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B), and if any, the A / B copolymer.

17. A laser-transparent molded part made of a laser-transparent polymer composition, obtainable by the process according to claim 15 or 16, wherein the laser-transparent polymer composition has a laser transparency of at least 25 %, measured at a thickness of 1 mm and at a wavelength of 980 nm by the method according to TMG3 as described herein above.

18. Use of a composition, or a molded part made thereof, comprising a combined amount of at least 35.2 wt.%, relative to the total weight of the composition, of(A) A polybutylene terephthalate resin (PBT resin); and(B) A di-alkali-metal alkali metal salt of norbornane-2,3-dicarboxylic acid, or a substituted derivative thereof; and / or- A polyester copolymer comprising repeat units, derived from the di-alkali-metal salt, or the substituted derivative thereof, incorporated in the PBT resin (referred to as A / B copolymer);- wherein component (B) is present, either as such or incorporated in the A / B copolymer, in an amount the range of 0.2 - 6 parts by weight (pbw), relative to 100 pbw of the combined amount of components (A) and (B), and, if any, the A / B copolymer; for laser-transmission welding.

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