body

.contenedor{
  width: 100%;
  margin: auto;
  overflow: hidden;
}

#slider {
  width: 2000px;
  height: 100px;

  background-image: url(imag/clientes.png);
  background-size: 100% 100%;

  animation: slider 30s infinite linear;

}

@keyframes slider {
  to {
    background-position: 2000px;
  }
}