Method for producing fiber-reinforced plastics

Patent metadata

Field	Value
Publication number	US-11833767-B2
Application number	US-202017607193-A
Country	US
Kind code	B2
Filing date	Apr 24, 2020
Priority date	Apr 29, 2019
Publication date	Dec 5, 2023
Grant date	Dec 5, 2023

Abstract

The invention relates to a pultrusion method for producing fiber-reinforced plastics, to carrying said method out by computer-assisted simulation and to a suitable underlying thermodynamic model.

First claim

What is claimed is:

1. A pultrusion method for the production of fiber-reinforced plastics profiles based on continuous fibers, on continuous-fiber bundles or on semifinished textile products, and on a liquid reactive-resin mixture, comprising:
i) drawing continuous fibers, continuous-fiber bundles or semifinished textile products through an injection box or a resin bath,
ii) charging, into the injection box or the resin bath, the liquid reactive-resin mixture to saturate the continuous fibers, the continuous-fiber bundles or the semifinished textile products,
iii) drawing the saturated continuous fibers, continuous-fiber bundles or semifinished textile products from the injection box or the resin bath into a chamber of a temperature-controllable die for the exothermic hardening of the reactive-resin mixture to form of the fiber-reinforced profile, and
iv) drawing the fiber-reinforced profile out of the chamber, wherein
a) in at least one preliminary experiment, the components of the reactive-resin mixture are mixed at a start temperature T 0 at a time t 0 , and at at least two further times t 1 and t 2 corresponding temperatures T 1 and T 2 are determined, and also reaction conversions r 1 and r 2 are determined during the exothermic reaction of the components in the reactive-resin mixture,
b) the measured values determined in a) are utilized for the determination of the parameters of a prescribed thermodynamic calculation model which describes the time-related changes of temperature and reaction conversion for any desired starting conditions for the reactive-resin mixture used,
c) the exothermic curing method described in step iii) is simulated in finite element method simulation software with the parameters determined in b) and with the thermodynamic calculation model and with the geometric data of the plastics profile and of the pultrusion die,
d) the simulation carried out in c) is used in an iterative method to determine optimized die temperatures at the entry into the chamber and in further sections of the chamber, said temperatures permitting the highest possible output rate while complying with prescribed quality features, and
e) the pultrusion is carried out with use of the optimized die temperatures in the chamber.

2. The pultrusion method as claimed in claim 1 , wherein step a) comprises:
a1) controlling the temperature of the components of the reactive-resin mixture to the temperature T 0 , and mixing said components at this temperature at the time t 0 ,
a2) measuring, at at least two further times t 1 and t 2 , the corresponding temperatures T 1 and T 2 , and
a3) calculating and/or measuring at least two reaction conversions r 1 and r 2 during the reaction, either at the times specified in a2) or at other times,
wherein in order to obtain the measurement data for the preliminary experiment, the step a) is carried out at least once for initial temperatures differing from T 0 .

3. The pultrusion method as claimed in claim 1 , wherein the following coupled differential equations are used as thermodynamic calculation model in step b):
dr/dt=k tot ·(1 −r ) n   (1)

1/ k tot =1/ k kin +1/ k diff   (2)

k kin =k 0 ·exp[− E a /RT]+k auto,0 ·exp[− E auto /RT]·r m   (3)

k diff =k diff,0 ·exp[− E diff /RT]· ( x diff +(1 −x diff )/(1+(exp[ r−r infl ]) P ))   (4)

dT/dt=ΔT ad ·dr/dt   (5)

where
r is reaction conversion (calculated and/or measured in step a) and utilized in step b) for parameter-determination in the thermodynamic model and simulated in step c)),
t is time (measured in step a) and prescribed in step c)),
k tot is overall rate constant (calculated in step b) and c) in accordance with equation (2)),
n is order of reaction (parameter calculated in step b)),
k kin is kinetic rate constant (in each case calculated in steps b) and c) in accordance with equation (3)),
k diff is diffusive rate constant (calculated in each case in steps b) and c) in accordance with equation (4)),
k 0 is kinetic pre-exponential factor (parameter calculated in step b)),
E a is kinetic activation energy (parameter calculated in step b)),
R is universal gas constant,
T is temperature of the reactive-resin mixture (measured in step a) and calculated in step c)),
k auto,0 is autocatalytic pre-exponential factor (parameter calculated in step b)),
E auto is autocatalytic activation energy (parameter calculated in step b)),
m is autocatalytic exponent (parameter calculated in step b)),
k diff,0 is diffusive pre-exponential factor (parameter calculated in step b)),
E diff is diffusive activation energy (parameter calculated in step b)),
x diff is value for the reduction of the diffusive rate constant (parameter calculated in step b)),
r infl is gelling conversion (parameter calculated in step b)),
p is diffusive exponent (parameter calculated in step b)), and
ΔT ad is adiabatic temperature increase (preferably measured in step a)),
and the values thus calculated are compared with the values measured in step a), and the procedure is iterated until agreement between the calculated values and the measured values is maximized.

4. The pultrusion method as claimed in claim 1 , wherein the following coupled differential equations are used as thermodynamic calculation model in step b):
dr/dt=k tot ·(1 −r ) n   (1)

1/ k tot =1/ k kin +1/ k diff   (2)

k kin =k B T/h 19 exp[−Δ H kin /RT+ΔS kin /R]+k B T/h· exp[−Δ H auto /RT+ΔS auto /R]·r m   (3)

k diff =k B T/h· exp[−Δ H diff /RT+ΔS diff /R] ·( x diff +(1 −x diff )/(1+(exp[ r−r infl ]) P ))   (4)

dT/dt=ΔT ad ·dr/dt   (5),

where
r is reaction conversion (calculated and/or measured in step a) and utilized in step b) for parameter-determination in the thermodynamic model and simulated in step c)),
t is time (measured in step a) and prescribed in step c)),
k tot is overall rate constant (calculated in step b) and c) in accordance with equation (2)),
n is order of reaction (parameter calculated in step b)),
k kin is kinetic rate constant (calculated in each case in steps b) and c) in accordance with equation (3)),
k diff is diffusive rate constant (calculated in each case in steps b) and c) in accordance with equation (4)),
k B is Boltzmann constant,
h is Planck constant,
ΔH kin is kinetic activation enthalpy (parameter calculated in step b)),
ΔS kin is kinetic activation entropy (parameter calculated in step b)),
R is universal gas constant,
T is temperature of the reactive-resin mixture (measured in step a) and calculated in step c)),
ΔH auto is autocatalytic activation enthalpy (parameter calculated in step b),
ΔS auto is autocatalytic activation entropy (parameter calculated in step b)),
m is autocatalytic exponent (parameter calculated in step b)),
ΔH diff is diffusive activation enthalpy (parameter calculated in step b)),
ΔS diff is diffusive activation entropy (parameter calculated in step b)),
x diff is value for the reduction of the diffusive rate constant (parameter calculated in step b)),
r infl is gelling conversion (parameter calculated in step b)),
p is diffusive exponent (parameter calculated in step b)), and
ΔT ad is adiabatic temperature increase (preferably measured in step a)),
and the values thus calculated are compared with the values measured in step a), and the procedure is iterated until agreement between the calculated values and the measured values is maximized.

5. The pultrusion method as claimed in claim 1 , wherein the prescribed quality features are:
(1) minimum conversion r min that is intended to be achieved at the end of the chamber in the plastics profile,
(2) average

Assignees

• Covestro Intellectual Property Gmbh & Co Kg

Inventors

• Froebel Sascha
• Kilian Benedikt
• Raffel Bolko
• Bruening Dirk

Classifications

• B29C70/523 Primary

  and impregnating the reinforcement in the die · CPC title

• B29C70/525 Primary

  Component parts, details or accessories; Auxiliary operations · CPC title