.search_btn.loading {
    background-color: #CCC;
    padding-right: 40px;
}
.search_btn.loading:after {
    content: "";
    position: absolute;
    border-radius: 100%;
    right: 6px;
    top: 50%;
    width: 0px;
    height: 0px;
    margin-top: -2px;
    border: 2px solid rgba(255,255,255,0.5);
    border-left-color: #FFF;
    border-top-color: #FFF;
    animation: spin .6s infinite linear, grow .3s forwards ease-out;
}
@keyframes spin {
    to {
        transform: rotate(359deg);
    }
}
@keyframes grow {
    to {
        width: 14px;
        height: 14px;
        margin-top: -8px;
        right: 13px;
    }
}