JPH0235053B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a crimped yarn made of polyester composite fibers (hereinafter sometimes referred to as polyester composite crimped yarn) and a method for producing the same. More specifically, the present invention relates to a polyester composite crimped yarn suitable for fabrics having the dual functions of water- and oil-repellency and elasticity with excellent durability such as wash resistance, and a method for producing the same. In recent years, demands on the elastic properties of woven and knitted materials have become even stronger. This is because the elasticity of woven and knitted materials has a close relationship with the comfort of wearing clothes, and those with good elasticity can easily follow the movements of various parts of the body, so there is no feeling of pressure. This is because it has the advantage of allowing activities to be carried out smoothly, and it also has the advantage of being resistant to wrinkles. Generally, when imparting stretchability to a woven or knitted fabric, since the constituent structure of the knitted fabric is loose, stretchability can be imparted relatively easily using ordinary false-twisted yarn, etc.; Since the constituent structure is denser than that of , it is not possible to obtain a fully satisfactory stretch fabric even if ordinary false twisted yarn is used. However, woven fabrics have other characteristics that knitted fabrics do not have, such as texture and luster, so it is important to take advantage of these characteristics and add stretch performance. has been desperately requested. The present inventor previously disclosed in Japanese Patent Application No. 56-141630 that a fabric having such stretchability exhibits an elongation rate of at least 15%, and that such a fabric is made of polybutylene terephthalate. (hereinafter abbreviated as PBT) and polyethylene terephthalate (hereinafter abbreviated as PBT)
It is a polyester composite fiber consisting of PET (abbreviated as PET) and is a composite crimped yarn that has been given false twist crimp, and the crimp rate (TC ₁₀ ) when treated with boiling water under a load of 10 mg/d is It was proposed that this could be obtained by using a crimped elastic yarn having a content of 8% or more. Fabrics using such crimped elastic yarns have powerful stretchability and are therefore suitable for fields that require stretchability, such as working clothing and sports clothing. However, it has been difficult to apply it to the field of clothing for outdoor sports, such as clothing for mountain climbing or clothing for skiing, because the fabric using the crimped elastic yarn lacks water and oil repellency. Therefore, the present inventor attempted to make a moisture-permeable waterproof fabric by laminating a porous film of polytetrafluoroethylene on this stretchable fabric, but since the porous film of such a laminated fabric lacks elasticity, The elasticity is greatly reduced, and since elastic stress is applied to the film, peeling occurs between the film and the fabric, resulting in a product that cannot be used for practical purposes. I couldn't come up with something that had both at the same time. From the above attempts, the present inventors believe that if water and oil repellency can be imparted to the threads constituting the stretchable fabric during the spinning process, a crimped elastic yarn reasonably imparted with water and oil repellency can be obtained. Moreover, we thought that we could obtain a fabric that has the functions of water and oil repellency and stretchability without any drawbacks such as peeling of the film due to expansion and contraction, and we conducted further tests. As a result, fluorine compounds exhibiting water and oil repellency (JP-A No. 55-90677, JP-A No. 52-5400, JP-A No. 52-5400,
No. 57-171760, JP-A-57-171761, JP-A-57-
PBT and PET bonded together (see Publication No. 171762)
It has been discovered that the above object can be achieved by a composite crimped elastic yarn consisting of the following, and the present invention has been achieved. That is, the present invention has a PBT component whose main component is polybutylene terephthalate, and a PBT component whose main component is polyethylene terephthalate.
A crimped yarn consisting of fibers in which a PET component is combined in a side-by-side type or eccentric sheath core type, and which has been given false twist crimp, and which simultaneously has the following (a) to (b). This is a crimped yarn made of polyester composite fiber that is characterized by satisfactory water and oil repellency and excellent washing resistance. (a) The crimp rate (TC ₁₀ ) when the yarn is treated with boiling water under a load of 10 mg/d is 8% or more. (b) A fluorine compound exhibiting water and oil repellency is fixed to the thread. Further, according to the present invention, the PBT component is composed of a PBT component whose main constituent component is polybutylene terephthalate, and a PBT component whose main constituent component is polyethylene terephthalate, and whose intrinsic viscosity [η] _PET is 0.55 or less.
0.05wt of a fluorine compound that exhibits water and oil repellency is added to a yarn made of fibers that are composite-spun with a PET component in a side-by-side type or eccentric sheath core type.
Provided is a method for producing a crimped yarn made of a polyester composite fiber, which comprises applying a single heater false-twisting process at a false-twisting heater temperature of 150° C. or more after imparting a polyester composite fiber of at least 10%. The present invention will be further explained. PBT and PET with durable water and oil repellency
It goes without saying that the fixed water and oil repellent agent itself exhibits sufficient water and oil repellency in the composite crimped elastic yarn consisting of It is important that it adsorbs to the surface of the constituent single fibers and forms a robust film. From this point of view, the water and oil repellent agent fixed to the crimped elastic yarn has a group in each molecule that exhibits water and oil repellency and a group that provides intermolecular cohesive force and adsorption force bonded to the mother nucleus. It is preferable to be there. in this regard,
As the water and oil repellent used in the present invention, fluorine compounds represented by the following general formula [] will be listed and explained.
The present invention is not limited to this. (However, X is fluorine or a perfluoroalkoxy group containing 1 to 6 carbon atoms, m is an arithmetic average of 2
Y is an integer from 2 to 20, and Y is an alkylene, cycloalkylene, or alkyleneoxy group consisting of 2 to 20 carbon atoms and containing at least 2 carbon atoms in the main chain. Z is oxygen or nitrogen; when Z is oxygen, p is 1; when Z is nitrogen, p is 2. R,
R' is H or a _C1 to _C14 hydrocarbon group, an aryl group, an aralkyl group, or a hydroxyalkyl group.
B is −CH ₂ R″CHOH or −
CH ₂ R″CHOCH ₂ R″CHOH, where R″ is hydrogen or a methyl group, or B is -CH ₂ CH(OH)CH ₂ Q
In this case, Q is a halogen atom, hydroxyl group, or nitrile group, and B is -CH ₂ CH (OH)
_{CH2OCH2CH (} OH) _CH2Q (Q is the same as above). t is 0.1 or 2, r and q are integers of at least 1, and the sum of r+q+t is 4. X(CF ₂ ) _n and Y are linear, branched or cyclic. Note that the substituents in the above general formula may be the same or different) (1) Due to the presence of the B group of -COOB in the fluorine compound, it is adsorbed to the surface of the single fiber and has a strong repellent property at the position closest to the synthetic fiber polymer. Forms a water and oil repellent film. Furthermore, even if such an agent is mixed into an oil agent and applied, the agent is distributed in the uppermost layer of the fiber surface, so the oil agent has the advantage that it can perform the same function as a conventional oil agent. The preferred structure of group B is -CH ₂ CH
(OH)CH ₂ Cl or -CH ₂ CH(OH)
_{CH2OCH2CH (} OH) _CH2Cl . (2) Furthermore, the perfluoroalkyl group in the molecule that minimizes surface free energy exhibits excellent water and oil repellency. (3) In addition, by introducing a sulfonamide structure into the fluorine compound molecule, the emulsion dispersibility is significantly improved, and a stable emulsion treatment liquid with almost no precipitation is produced in the emulsion circulation pipe and emulsion tank. This makes it easier to form a uniform, durable water- and oil-repellent coating. In addition, it is particularly preferable that Z in the above general formula [] is oxygen from the viewpoint of ease of synthesis, and also to maximize the effects of adsorption to fibers, water repellency, oil repellency, and improvement of emulsification and dispersibility in a well-balanced manner. In order to achieve this effect, it is particularly preferable that q and r be q=r=2. Furthermore, the formula

If the R group in [Formula] has a large number of constituent carbon atoms, it will disturb the arrangement of the fluorine compound groups and have a negative effect on water and oil repellency, so it is better to have a smaller number of constituent carbon atoms. Particularly preferred are groups. (4) Moreover, the hydrocarbon group in the form of -(CO ₂ R′) _t is the above-mentioned -
Although its function is lower than that of groups containing COOB or SO ₂ N, -(CO ₂ R') itself may lower the molecular specific gravity of the agent and facilitate emulsification and dispersibility. In addition, the composite crimped yarn made of PBT and PET to which such an agent is fixed has a crimp rate (TC ₁₀ ) of 8% or more, preferably 10% or more when treated with boiling water under a load of 10 mg/d. There is a need. Here, if TC ₁₀ is less than 8%, the fabric using this crimped yarn exhibits water and oil repellency as described above, but its elongation rate is less than 15% and it cannot be called a stretch fabric. become. Furthermore, even stretch fabrics made of crimped yarns to which the above agent has been applied and have a TC ₁₀ of 8% or more are required to exhibit water and oil repellency with excellent washing resistance. That is, the water repellency of the fabric after washing five times is 300 seconds or more, and the oil repellency is also grade 5 or higher. Here, if the water repellency of the fabric after 5 washes is less than 300 seconds or the oil repellency is less than grade 5, it cannot be put to practical use as outdoor sports clothing, which is the main use of such fabrics. The water repellency and oil repellency referred to herein are measured by the following method. (a) Water repellency Use a 20% by volume aqueous solution of isopropyl alcohol. Place one drop on the sample and measure the time (seconds) until the water drop disappears. (b) Oil repellency Conforms to AATCC118-1972. A drop of the reagent shown in Table 1 is gently dropped onto the horizontally spread surface of the sample, and the state of penetration is judged after 3 seconds.

[Table] In order to obtain the crimped yarn explained above,
It is important to add a specific amount of a fluorine compound that exhibits water and oil repellency to a composite spun yarn of PBT and PET with a specific intrinsic viscosity, and then false twist it under specific conditions. In the present invention, it is necessary that _the intrinsic viscosity [η] of the PET component, which is one of the components to be composite-spun with PBT, is 0.55 or less. Here, [η] _PET is
If it exceeds 0.55, the heat shrinkage stress of the PET component will be
Compared to the PBT component, the tension heat setting performed to reduce the stress sufficiently is insufficient, and the PET component has a large residual heat shrinkage stress. Therefore, the crimped yarn obtained has a TC ₁₀ of less than 8%. on the other hand,
Intrinsic viscosity of PBT component [η] _PBT is preferably 0.7 or more, particularly preferably 0.8 or more. This is because, with such a high viscosity PBT component, the degree of orientation during spinning is higher than that of the PET component, and the mechanical properties such as crimp and expansion after subsequent stretching or false twisting are fully demonstrated. This is because it can be forced. Considering the spinning stability, the composite ratio of such composite fibers is such that the ratio of PBT component is 30 to 70%, preferably 35 to 65%, and the ratio of PET component is 70 to 30%, preferably 65 to 35%. The ratio is preferred. The composite spun yarn is wound at a constant speed via a roller. Next, it is stretched at a predetermined magnification and then subjected to false twisting. At this time, an undrawn yarn that has been wound at a relatively high spinning take-off speed, for example, 2000 m/mm or more, may be subjected to the drawing false twisting process. Also, the amount of fluorine compound is 0.05wt relative to the yarn weight.
% or more, preferably 0.1 wt% or more, before false twisting. If the amount of the fluorine compound applied is less than 0.05 wt%, sufficient water and oil repellency cannot be exhibited. It is preferable to apply such a fluorine compound by mixing it into an oil agent, particularly a spinning oil agent, and applying it together with the spinning oil agent. This is because the fluorine compound is sufficiently adsorbed onto the fiber surface by being heated to a high temperature in the subsequent process, thereby improving the durability of water and oil repellency. Examples of oils used at this time include:
Any material may be used as long as it satisfies various properties required in each process, such as lubricity, antistatic property, extensibility, and heat resistance that can withstand thermal decomposition of the oil on the heater. As the optimal lubricant component, an ester-based smoothing agent with excellent heat resistance is preferable. For example, monobasic acid esters, dibasic acid esters, polybasic acid esters,
The main component is ester smoothing agents such as lycole esters, polyhydric alcohol esters, and aromatic carboxylic acid esters, or a combination thereof, but mineral oil, polypropylene glycol, polyisobutylene, polybran, or polyester is used as the main component. May contain ether. Such smoothing agents include alkyl phosphates, alkyl sulfonates, alkyl sulfosuccinates, alkyl sulfates and/or their alkylene oxide adducts, which also serve as nonionic emulsifiers and antistatic properties.
Alternatively, if it is used in combination with an alkali metal salt of a higher fatty acid, an ammonium salt, a cationic surfactant, or an amphoteric surfactant, etc., and satisfies the emulsion stability of the finishing agent containing the fluorine compound, the spinning process, and the post-processing process. For example, there are no particular restrictions on oils. Furthermore, the yarn to which the fluorine compound has been added in this way has a false twisting heater temperature of 150°C or higher, preferably
Single heater false twisting at 150-210°C is required. Here, when the false twisting heater temperature is less than 150°C, the TC ₁₀ of the obtained crimped yarn is less than 8%. Moreover, if the yarn is not heated to 150°C or higher during the false twisting process after the fluorine compound is applied, the durability of the water and oil repellency will also be poor. In addition, in the heater false twisting process in which a relaxation heat treatment is performed after false twisting, the TC ₁₀ is less than 8%. The PBT component referred to in the present invention is preferably composed of butylene terephthalate in an amount of 80 mol% or more, particularly preferably 90 mol% or more of repeating units. When the content of butylene terephthalate is less than 80 mol%, there is a tendency for dyeing properties such as washing resistance and weather resistance to decrease. On the other hand, the PET component is preferably composed of ethylene terephthalate in an amount of 80 mol% or more, particularly preferably 90 mol% or more of repeating units. When the ethylene terephthalate content is less than 80 mol%, the crimp rate TC ₁₀ of the resulting crimped yarn also tends to be less than 8%. The above-mentioned polybutylene terephthalate contains a third component in a proportion of 20 mol % or less, preferably 10 mol % or less, such as dicarboxylic acids such as isophthalic acid, phthalic acid, methyl terephthalic acid, and adipic acid, ethylene glycol, and trimethylene glycol. , neopentyl glycol and other diglycols may be copolymerized, and may also contain small amounts of other polymers, titanium oxide, matting agents such as calcium carbonate, and other known additives. In addition, polyethylene terephthalate contains a third component in a proportion of 20 mol% or less, preferably 10 mol% or less,
For example, the aforementioned dicarboxylic acids and diglycols such as trimethylene glycol, tetramethylene glycol, and neopentyl glycol may be copolymerized, as well as small amounts of other polymers, matting agents such as titanium oxide, calcium carbonate, etc. It may also contain other known additives. The fabric obtained using the crimped yarn of the present invention described above is a stretch fabric that has both an elasticity of 15% or more and durable water and oil repellency. The present invention will be explained below with reference to Examples.
Crinkage rate when subjected to boiling water treatment under a load of 10mg/d
A method for measuring TC ₁₀ , [η] _PBT , [η] _PET of spun yarn, and fabric elongation rate will be explained. (b) Crimp ratio when subjected to boiling water treatment under a load of 10 mg/de A TC ₁₀ sample is wound around a skein frame under a tension of 50 mg/de to make a skein of approximately 3000 de. After making the skein, a load of 2 mg/de + 200 mg/de is applied to one end of the skein, and the length l ₀ (cm) is measured after 1 minute has elapsed.
Next, the load of 200 mg/de was removed and the load of 8 mg/de was applied (i.e., the sample was loaded with a load of 10 mg/de) in boiling water at 100°C.
Process for 20 minutes. Immediately after boiling water treatment, remove the entire load and allow to air dry in a free condition for 24 hours. A load of 2 mg/de + 200 mg/de is applied again to the air-dried sample, and the length l ₁ (cm) is measured after 1 minute has elapsed. Then, the load of 200 mg/de was removed, and 1
Measure the length l ₂ after a minute has elapsed and use the following formula to determine the crimp rate.
Calculate TC ₁₀ . TC ₁₀ (%)=l ₁ −l ₂ /l ₀ ×100 The above measurement must be carried out after three days or more have elapsed after the production of the crimped yarn. (b) Intrinsic viscosity of the PBT component and _PET component of the spun thread [η] _PBT , [η] 35 It was measured in a solution at ℃. (c) Fabric elongation rate Prepare a sample with a length of 30 cm and a width of 5 cm in the weft direction of the fabric, and mark 100 mm from the center of the sample in the length direction and toward both ends (length between marks) is 200mm). Width 60 mm at one end of this sample
Fix it with a chuck of mm, then attach a load of 1.5 kg to the other end, and after leaving it for 5 seconds, measure the length L (mm) and calculate it using the following formula. Fabric elongation rate (%) = L-200/200×100 Example Using a commercially available composite spinning machine, polybutylene terephthalate having an intrinsic viscosity of 0.86 and polyethylene terephthalate containing 0.3% by weight of titanium oxide and having an intrinsic viscosity of 0.47 were prepared. and melted respectively,
The discharge ratio of PBT and PET components is 50:
The spinning speed was 2500 m/min. The fluorine compound used in this example is a mixture of pyromellitic acid esters having the following structure. For convenience, this pyromellitic acid ester mixture is hereinafter referred to as fluorine compound composition [F]. A mixture of fluorine compound composition [F] with an emulsifier and anion (undiluted solution mixture-1) and a mixture of coconut oil as a smoothing agent and an emulsifier (undiluted solution mixture-2) were heated at 80°C.
First, stock solution mixture-2 was stirred and added to water at 80°C, and then stock solution mixture-1 was added and emulsified and dispersed. After uniform stirring, the mixture was cooled to 35°C. Table 2 shows the spinning finishing oils obtained in this way.
A stable emulsion was prepared by adjusting the concentration of the oil agent to 20% by weight. After spinning and solidifying, the spinning finishers shown in Table 2 were applied to the undrawn polyester composite yarn in an oil content of about 1.0% by weight.

[Table] Furthermore, after heating the composite yarn to approximately 120℃ and drawing it using a commercially available one-stage drawing machine, the cutting elongation was 30.
%. Next, the obtained composite yarn was twisted with a number of twists of 2650T/1 using a commercially available single heater spindle false twister.
False twisting was carried out with M at various heater temperatures shown in Table 3 to obtain polyester composite crimped yarns. The false twisting speed was 120 m/min, and the ratio between the yarn supply speed and take-off speed was adjusted so that the yarn breakage elongation after false twisting was approximately 25%. Furthermore, the obtained crimped yarn was woven using a commercially available ordinary loom.
Warp density: 26.5 threads/cm, weft density: 25.9 threads/cm, commercially available polyester single heater false twisted yarn for warp threads
A plain woven fabric was prepared using 150 denier 48 filament yarn and the crimped yarn prepared above as the weft. Next, 1 g each of score roll and soda ash was added to the plain fabric, and acetic acid was added to relax the fabric in warm water at 70°C adjusted to 6.7 for 20 minutes, followed by presetting in hot air at 180°C for 45 seconds. . After dyeing, the fabric was immersed in a dye bath adjusted to PH=6.4 at 130°C for 45 minutes, followed by finishing setting in hot air at 160°C for 45 seconds to obtain a fabric. Table 3 also shows the results of measuring the elongation, water repellency, and oil repellency of this fabric.

[Table] In No. 1, the false twisting heater temperature is as low as 140℃, so
The crimp rate is as low as 7.0%, and therefore it is not possible to obtain the preferred elongation rate of 15% for a stretch fabric.
In addition, although water and oil repellency initially show good values, the durability deteriorates as the number of washings increases.
Water and oil repellency is greatly reduced. On the other hand, in No. 7 and 8
Although it has a high TC ₁₀ and is preferred as a stretch fabric, its water and oil repellency is at a low level. (In No. 7, the amount of fluorine compound composition [F] attached is small, and its durability is also affected.) In Examples No. 2 to 6, the crimp ratio TC ₁₀ is 8% or more, and it can be used as a stretch fabric. It maintains a preferable elasticity of 15% or more, and also has high levels of water repellency, oil repellency, and durability. Comparative Example Spinning, stretching, and false twisting were performed in the same manner as in Example No. 4, except that the PET component [η] _PET was 0.61. The TC ₁₀ of the obtained processed yarn was 6.6%. When we measured the elongation rate and water and oil repellency of a plain fabric using such processed yarn, the water repellency was 300 seconds or more for both L ₀ and L ₅ , and the oil repellency was also 6th grade for L ₀ and 5th grade for L ₅ . It was hot. However, the elongation rate was 12.4%, and the fabric was not stretchable.

Claims (1)

[Claims] 1. A PBT component whose main component is polybutylene terephthalate, and a PET component whose main component is polyethylene terephthalate,
A crimped yarn consisting of fibers composited in a side-by-side type or eccentric sheath core type and having been given false twist crimp, which simultaneously satisfies the following (a) to (b), and A crimped yarn made of polyester composite fiber that exhibits water and oil repellency with excellent washing resistance. (a) The crimp rate (TC ₁₀ ) when the yarn is treated with boiling water under a load of 10 mg/d is 8% or more. (b) A fluorine compound exhibiting water and oil repellency is fixed to the thread. 2. A crimped yarn comprising a polyester composite fiber according to claim 1, wherein the fluorine compound is a fluorine compound represented by the following general formula []. (However, X is fluorine or a perfluoroalkoxy group containing 1 to 6 carbon atoms, m is an arithmetic average of 2
Y is an integer from 2 to 20, and Y is an alkylene, cycloalkylene, or alkyleneoxy group consisting of 2 to 20 carbon atoms and containing at least 2 carbon atoms in the main chain. Z is oxygen or nitrogen, and if Z is oxygen, p is 1,
When Z is nitrogen, p is 2. R, R' are H or
A _C1 to _C14 hydrocarbon group, an aryl group, an aralkyl group, or a hydroxyalkyl group. B is-
CH ₂ R″CHOH or −CH ₂ R″CHOCH ₂ R″CHOH
In this case, R'' is hydrogen or a methyl group, or B is -CH ₂ CH (OH) CH ₂ Q, in which case Q is a halogen atom, a hydroxyl group, or a nitrile group, and furthermore, B is -
_CH2CH (OH) _CH2OCH2CH ( _OH ) _CH2Q . (Q is the same as above). t is 0, 1 or 2
, r and q are integers of at least 1 and r+q+
The total of t is 4. X(CF ₂ ) _n and Y are straight chains,
Branched or cyclic. In addition, the substituents in the above general formula may be the same or different. ) 3 A crimped yarn comprising a polyester composite fiber according to claim 2, wherein Z in the general formula [ ] is oxygen and the substituent R on the nitrogen atom is a propyl group. 4 q, r and t of general formula [] are q=r=2,
A crimped yarn made of the polyester composite fiber according to claim 3, wherein t=0. 5 A PBT component whose main component is polybutylene terephthalate and a PET component whose main component is polyethylene terephthalate and whose intrinsic viscosity [η] _PET is 0.55 or less are combined into a side-by-side type or eccentric sheath core. It is characterized by adding 0.05wt% or more of a fluorine compound that exhibits water and oil repellency to a yarn made of composite-spun fibers in a mold, and then subjecting it to single heater false twisting at a false twisting heater temperature of 150°C or higher. A method for producing crimped yarn made from polyester composite fibers. 6. The method for producing a crimped yarn made of polyester composite fiber according to claim 5, wherein the fluorine compound is a fluorine compound represented by the following general formula []. (However, X is fluorine or a perfluoroalkoxy group containing 1 to 6 carbon atoms, m is an arithmetic average of 2
Y is an integer from 2 to 20, and Y is an alkylene, cycloalkylene, or alkyleneoxy group consisting of 2 to 20 carbon atoms and containing at least 2 carbon atoms in the main chain. Z is oxygen or nitrogen, and if Z is oxygen, p is 1,
When Z is nitrogen, p is 2. R, R' are H or
A _C1 to _C14 hydrocarbon group, an aryl group, an aralkyl group, or a hydroxyalkyl group. B is-
CH ₂ R″CHOH or −CH ₂ R″CHOCH ₂ R″CHOH
In this case, R'' is hydrogen or a methyl group, or B is -CH ₂ CH (OH) CH ₂ Q, in which case Q is a halogen atom, a hydroxyl group, or a nitrile group, and furthermore, B is -
_CH2CH (OH) _CH2OCH2CH ( _OH ) _CH2Q . (Q is the same as above). t is 0, 1 or 2
, r and q are integers of at least 1 and r+q+
The total of t is 4. X(CF ₂ ) _n and Y are straight chains,
Branched or cyclic. In addition, the substituents in the above general formula may be the same or different. ) 7. A method for producing a crimped yarn made of polyester composite fiber according to claim 5, wherein the fluorine compound is applied together with a spinning oil. 8. The method for producing a crimped yarn comprising a polyester composite fiber according to claim 6, wherein Z in the general formula [ ] is oxygen and the substituent R on the nitrogen atom is a propyl group. 9 q, r and t of general formula [] are q=r=2,
A method for producing a crimped yarn made of polyester composite fiber according to claim 8, wherein t=0.